One victim is receiving medical treatment, according to law enforcement and hospital officials.

A student at Pownal Elementary in Pownal brought an unloaded 9mm handgun and 67 rounds of ammunition to school on Wednesday, authorities said.

A hospital employee shot a co-worker multiple times in Troy, Michigan, at the building's parking garage on Thursday in a "targeted attack," according to police.

Law enforcement officials apprehended a man near the CIA headquarters in McLean, Virginia, following a tense standoff that lasted for several hours on Wednesday.

A CIA spokesperson said law enforcement responded to an "incident" outside CIA headquarters, located in Fairfax County, Virginia.

A CIA spokesperson said law enforcement responded to an "incident" outside CIA Headquarters, located in Fairfax County.

Ashley Van Hemert tells "20/20" about the fateful 2018 night her roommate's estranged husband barged into their home, killed his wife and left her for dead.

Authorities are searching for the man who broke into a Los Angeles-area house and gunned down a father while his wife and son were home, officials said.

At least one person has been shot outside Chicago O'Hare International Airport early Wednesday morning, police said.

A 25-year-old man was shot near the arrivals area of Terminal 2 early Wednesday morning during an altercation involving multiple people, police said.

A homicide investigation is underway after a reporter for the conspiracy theory platform InfoWars was shot dead outside his apartment complex in Austin, Texas.

Officials said the online video showed the teen with several guns, which later turned out to be highly realistic Airsoft replicas, claiming he was going to "shoot up" a school.

A 14-year-old is facing multiple charges, including murder, after a New Jersey detective was fatally shot. At least four others were detained. ABC News' Ike Ejiochi reports.

A 14-year-old boy has been arrested and charged with murder in the death of a Newark, New Jersey, police officer after shots were exchanged between police and a group on Friday night.

At least 12 people have been injured in a shooting at a pub in Toronto on Friday night, police said.

At least 12 people have been injured in a shooting at a pub in Toronto on Friday night, police said.

Canadian police say a dozen people were injured in a shooting at a pub in eastern Toronto

A Newark, New Jersey, police officer has been killed and another was wounded in a shooting

Police responded to a shooting incident at a USPS Processing and Distribution Center in Washington. An adult male victim succumbed to gunshots while the shooter fled.

Southern University and A&M College is a historically Black university system located in Baton Rouge, Louisiana.

Hundreds of fellow officers, as well as friends and family, showed up to remember West York police officer Andrew Duarte after he was shot while responding to an incident at a hospital.

Authorities say a hooded suspect was seen on surveillance footage firing into the Lake Oswego, Oregon, home of SAIF CEO Chip Terhune. No one was hurt in the incident.

A convicted felon "executed" two Virginia police officers at point-blank range following a weekend traffic stop, authorities said.

The suspect, Diogenes Archangel Ortiz, entered the hospital with handgun and zip ties Saturday morning and took several staff members hostage, state officials said.

ABC New’s Christiane Cordero provides the latest updates in a deadly hospital hostage situation in Pennsylvania.

One officer was killed and five people were wounded in a hostage situation and shootout at a Pennsylvania hospital, state officials said.

Police say a suspect carrying a handgun and zip ties entered the ICU at UPMC Memorial Hospital in York, Pennsylvania, and took several staff members hostage.

Multiple people were injured in a shooting at a hospital in York County, Pennsylvania, on Saturday, according to law enforcement. No patients were injured, the hospital said.

A shooting early Saturday morning near an Air Force Base in Albuquerque, New Mexico, left one airman dead and another wounded, authorities said.

The male victim died at the scene. Two females died at the hospital.

Three people were shot and killed in a parking lot outside a driver's licensing office in Louisville, Kentucky, on Friday, police said.

Andrew Lester, the man who pleaded guilty to felony assault in the second degree for the shooting of Ralph Yarl, died while awaiting sentencing.

The FBI arrested two teenage girls plotting a “mass casualty attack” using pipe bombs and guns targeting Memorial High School in Harris County, Texas, police said.

A Florida man has been arrested and charged for shooting 17 bullets at two men who he thought were Palestinians.

ABC News’ Linsey Davis speaks to the mother and aunt of now-18-year-old Ralph Yarl who was shot almost two years ago after ringing Andrew Lester’s doorbell, not realizing he was at the wrong house.

Andrew Lester pleaded guilty to second-degree assault charges against Ralph Yarl in a 10-minute Missouri court hearing on Friday.

A tip to an anonymous hotline leads to arrest of teenager in central Indiana who police say was plotting to carry out a mass shooting at her high school on Friday.

A former rapper is advocating for violent teens to receive a second chance at life.

One person was killed and five others were injured in a shooting at a facility in New Albany, Ohio, police said.

The firearm found on the suspect in the murder of the UnitedHealthcare CEO is believed to have been an untraceable ghost gun, according to police.

"It is a very painful day for all of Sweden," Prime Minister Ulf Kristersson said in a statement posted on social media.

The suspect is among those killed in the shooting, according to a Swedish police spokesperson.

Two people were shot and killed inside a grocery store in Indiana on Monday, officials told ABC News.

Two people were shot and killed inside a grocery store in Indiana on Monday, officials told ABC News.

The gunmen who shot and killed a 7-year-old boy, Breon Allen, are at large, and a $18,000 reward is being offered for information leading to their arrests.

Authorities in Florida are searching for the gunmen who "callously" shot and killed a 7-year-old boy. An $18,000 reward is available for information leading to arrests.

An arrest has been made in the shooting of a U.S. Border Patrol agent during a traffic stop in Vermont, with unusual details about the suspects' alleged actions in the arrest affidavit.

A 17-year-old boy who opened fire in his Nashville high school's cafeteria fired a total of 10 shots from a 9 mm pistol within 17 seconds of entering the room.

Seven police officers were shot during an armed standoff in San Antonio on Wednesday night while responding to a call about a possible suicide.

A social media account connected to the Nashville high school shooting suspect may have been in contact with the suspected Wisconsin school shooter's account.