'It’s a tough place to be in right now': US police face scrutiny and violence amid angry George Floyd protests

While police officers across the country have come under scrutiny for a series of ugly encounters with protesters demanding justice in the wake of the white officer-involved killing of African American George Floyd in Minneapolis, law enforcement veterans say controversial videos capturing what appears to be excessive use of force don't tell the whole story or take into account agitators and brazen criminals capitalizing on the chaos.

Demonstrations across the country have turned violent and deadly for U.S. police officers who find themselves walking a delicate balance between protecting protesters' First Amendment rights and guarding property from being looted and destroyed.

A police officer was shot and critically wounded in Las Vegas Monday night when a peaceful demonstration turned violent, authorities said. The officer, whose name was not immediately released, was engaging with protesters near the Circus Circus Hotel & Casino when the shooting occurred, officials said. In a second incident in Las Vegas, police shot a suspect they alleged was wielding multiple weapons outside a courthouse. The man was taken to a hospital, where he was pronounced dead.

In St. Louis, four officers were shot and wounded during a protest that drew several thousand people and turned into a free-for-all in which fireworks and gas were hurled at police and mobs began looting businesses, officials said.

In New York City, video emerged of an officer being attacked by a group of men in the Bronx who appeared to throw a heavy object at the officer while he was on the ground. Several officers were struck by cars Monday night and there was widespread looting and vandalism across the city, including at luxury stores in Rockefeller Center and the Upper East Side, according to the New York Police Department (NYPD). Nearly 700 arrests were made Monday night and into Tuesday morning in New York, where a curfew went into effect at 11 p.m. Monday.

On Friday night, Dave Patrick Underwood, a Federal Protective Service contract officer, was shot and killed at the federal building in Oakland, California. Underwood was slain while on duty and the FBI says shots were fired by an unidentified person in a vehicle. Authorities are investigating whether it was tied to a protest.

“This is what we’re looking at right now. It’s a tough place to be in right now," Robert Boyce, the retired chief of detectives of the NYPD and an ABC News contributor, said of police on the front lines of American discord.

Eddie Johnson, the former Chicago police superintendent, added that police are juggling two volatile situations: legitimate protesters venting their anger in a peaceful way and violent agitators bent on destruction.

"That’s unfortunate because it takes away from the real message of how police interact with people in general, especially people of color, African Americans," Johnson told ABC News. "It’s completely taken away from that message and now all the focus is on violence and it’s a shame."

Nearly 800 people were arrested in Chicago during protests over the weekend when groups split off from demonstrations and began looting and vandalizing businesses, police said.

On Monday afternoon, President Donald Trump, who critics say has fueled some of the violence with inflammatory tweets suggesting protesters could be shot for looting, said he has seen enough and threatened to use the military to quell the violence. In a White House Rose Garden speech, with protesters assembled right outside the gates, Trump implored governors across the nation to boost the presence of National Guard troops in cities to "dominate the streets."

"As we speak, I am dispatching thousands and thousands of heavily armed soldiers, military personnel and law enforcement officers to stop the rioting, looting, vandalism, assaults and the wanton destruction of property," he said. "We will end it now."

The president said he is an "ally of all peaceful protesters" while at the same time the National Guard and police were using force to disperse a peaceful protest outside the White House gates so Trump could cross the street to a vandalized St. John's Episcopal Church to be photographed holding a Bible.

Jarrod Burguan, the former police chief of San Bernardino, California, and an ABC News contributor, said police commanders nationwide are weighing how much leeway to give legitimate protesters. But when conditions deteriorate, decisions have to be made to protect lives and property, he said.

"When things turn violent and when things have reached kind of the point that we are at now, you realize that the only way to really, truly put it down is to truly respond with force and find a way to stop the looting and stop the violence that's happening," Burguan said in an interview on the ABC News podcast "Start Here."

Caught on video

But in some cases, police officers trying to keep a lid on rising tensions while allowing peaceful protests to go on have been caught on camera seemingly committing the very acts people are protesting against.

In Seattle, a video surfaced over the weekend showing a police officer with his knee on the neck of a pinned protester, an act that was similar to circumstances surrounding Floyd's May 25 death. Protesters screamed for the officer to remove his knee until a colleague pushed it away. The incident is under investigation.

In Atlanta, two police officers were fired and three others were yanked off the streets and placed on desk duty after they were caught on video deploying stun guns on two black college students who were in a car simply driving home from a protest, authorities said.

In Fort Lauderdale, Florida, a police officer was suspended after a video showed him pushing a kneeling black woman to the ground during protests.

In New York, police officers are under investigation after video footage surfaced of them using their vans to ram a crowd of protesters in Brooklyn after demonstrators hurled projectiles at their vehicles and used a metal barricade to block their path. In a separate incident, a New York City police officer is now the subject of an internal investigation after he was recorded on video aggressively shoving a female protester to the ground for apparently getting too close to him.

"One of your biggest fears is that it only takes one officer on that front line to lose his cool because ... he's got people yelling at him," Burguan said. "Maybe you got a water bottle thrown at him whatever it might be. It just takes one officer to lose their cool and pull out their pepper spray or start poking people with their baton or start doing things that are gonna agitate the crowd that's going to make your job infinitely more difficult. And I guarantee you that there are chiefs all over the country that are going to evaluate the actions of their specific officers and how things went down. And there's going to be that due process [in] those investigations that happen on the backside."

Not only do officers assigned to skirmish lines have to deal with protesters screaming obscenities in their faces, they also have to cope with agitators who infiltrate legitimate demonstrations in order to wreak havoc and career criminals bent on looting businesses, Boyce said.

"To be quite honest with you, these anarchists are very well organized, they’re anti-everything -- anti-religion, anti-capitalism, anti-globalism, you name it they’re anti," he continued. "They want a complete breakdown of structure and that’s what we’re kind of going through right now."

'Professional agitator'

Federal prosecutors in Brooklyn, New York, identified one of three protesters arrested on suspicion of tossing Molotov cocktails at NYPD vehicles as someone known to police across the county as a "professional agitator." Prosecutors, according to court records, say Samantha Shader has previously been arrested 11 times in 11 different states since 2011 for allegedly committing acts of violence and resisting arrest.

Shrader was charged with federal crimes of causing damage by fire and explosives to police vehicles. She has not yet entered a plea and remains in federal custody.

Two other suspects charged in the firebombings of police vehicles, Colinford Mattis and Urooj Rahma, are licensed attorneys who have attended prestigious universities and law schools, according to court records. They, too, were charged with federal crimes of causing damage by fire and explosives to police vehicles, but have yet to enter a plea and remain in federal custody.

“As such, the defendants were well aware of the severity of their criminal conduct when they decided to hurl a Molotov cocktail at an NYPD vehicle and to incite others to do the same," federal prosecutors said in court documents.

Shader was photographed in a car holding what appeared to be a Molotov cocktail at the scene of one of the New York firebombings, authorities said.

“The defendant’s criminal conduct was extraordinarily serious,” prosecutors alleged of Shader in court papers. “She hurled a Molotov cocktail at an NYPD vehicle with emergency lights on and occupied by four police officers, causing damage to the vehicle and putting the officers’ lives in serious danger.”

Boyce, who retired from the NYPD in 2017 after a 35-year career with the department, said on Friday night alone 47 police vehicles were torched and 30 officers were injured when peaceful protests turned violent.

He said that while he empathizes with protesters seeking justice for Floyd's killing, he added that the demonstrations are drawing a more nefarious element and police officers are often caught in the middle and often goaded into ambushes or provoked into aggressive behavior that gets caught on viral videos.

He said roving bands of well-organized anarchists have been stockpiling bricks, bottles and gasoline bombs in areas where they know protests will occur and then striking at the optimum moment, usually when news media is on hand to witness their actions.

"You have Molotov cocktails, you have bricks and bottles being thrown at police officers," Boyce said. “These are riots right now. This has been completely hijacked."

U.S. Attorney General William Barr used similar language on Saturday to describe the chaos on the streets of American cities in the wake of the Floyd killing.

“The voices of peaceful protests are being hijacked by violent radical elements,” Barr said in a televised statement at the Department of Justice.

“Groups of outside radicals and agitators are exploiting the situation to pursue their own separate and violent agenda. In many places it appears the violence is planned, organized and driven by anarchic and left extremist groups, far-left extremist groups using Antifa-like tactics, many of whom traveled from outside the state to promote the violence,” Barr said.

Chemical attacks

The Homeland Security Bureau Southeast Florida issued a bulletin on Sunday to federal and state authorities in South Florida listing the incidents in which police officers have been attacked with unknown chemicals during protests over the weekend. In Philadelphia on Saturday, police officers reported sustaining chemical burns during protests, according to the agency, while in Miami people were spotted mixing chemicals in water bottles during a demonstration there. In Fort Lauderdale, dozens of people pelted police with plastic bottles containing unknown fluid, the agency reported.

"After the Molotov cocktail attack Friday night, law enforcement remains concerned that protests could give cover to 'agitators' looking to use chemicals or gasoline to injure police," according to the bulletin obtained by ABC News.

“I think that people forget, citizens forget these cops are human too and they don’t get paid to get spit on, get bricks thrown at them and the new thing of the day is to throw water bottles at them," Johnson said. "Now that water bottle could contain water or various other things. They don’t get paid to be punching bags out there. But the majority of the cops do a really good job at showing restraint."

Johnson said that during his 31 years in law enforcement, he has encountered groups of anarchists crossing state lines to cause trouble in Chicago.

"They would come from out of town with the one thought of agitating police and what they do is they bait police into doing something or being overly aggressive then they sue," Johnson said. "And they use that money to continue traveling around the country and causing headaches everywhere they go. So we do have professional people who travel around the country and do nothing but stir up these incidents."

He said he is encouraged to see instances across the country in which legitimate protesters have called out agitators in the act of causing disturbances.

“The real protesters who are trying to change things, they don't want that message getting clouded with agitators out there just to create chaos," Johnson said. "Our real protesters aren’t trying to clash with the police. They’re trying to get a message out there and they don’t want that message to get conflated with violence."

Johnson noted that many U.S. officers on the front lines of the protests are black and face additional dynamics of weighing their own experience with racism in law enforcement agencies and doing their jobs and watching the backs of their colleagues.

“If you saw that video of George Floyd's life being snuffed out and you think that’s OK and you're a cop then you need to turn in your badge right away because there’s nothing that I saw that was right about that," said Johnson, who is African American. "Now having said that, I understand people protesting so vigorously because we do have to have change, we do have to create a culture that everybody is looked at equally, not just treated equally, but looked at equally. And their lives have the same value as anybody else's life. So I empathize with that."

The Major Cities Chiefs Association, an organization comprised of police chiefs from the nation's largest cities, released a letter to its members on Monday, saying, "We need to hear what America is telling us right now."

"The death of George Floyd was, by any measure of professional policing unnecessary, avoidable and criminal," the letter says.

The letter referred to other notable cases in which black lives have been "unjustly lost" to the hands of police, including Eric Garner in New York in 2014, Walter Scott in South Carolina in 2015 and Philando Castile in Minnesota in 2016.

"Each of these cases raised different concerns, but collectively they add new and painful chapters to our history that compels all of us to take inventory and be held accountable," the letter says.

"It will take strong leadership from all of us as well as collaborative partnerships from leaders from all walks of life and all levels," the letter continues. "Actions matter and so do words. Provocative statements create tension that lead to danger for police officers and the public. During challenging times, leaders need to reassure and calm, not instigate and stoke discord. Let us be the example for all leaders to follow. More than anything, this is a time for us to help facilitate healing, learning, listening and then dialogue, particularly in communities of color."

ABC News' Josh Margolin and Aaron Katersky contributed to this report.