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.

Police in Pennsylvania are searching for the gunman wanted for killing a young man and wounding his mother during a home invasion in an upscale Philadelphia suburb.

A police officer was fatally shot Sunday night while conducting a traffic stop in Terrell, Texas, police said.

A mother is in critical condition and her son has been killed in a home invasion shooting in a Philadelphia suburb. The suspect is at large and has not been identified, officials said.

Investigators provided more information on the shooting at a Christian school in California that has left two kindergarteners in critical but stable condition.

One person has been killed and three others injured, including the suspected gunman, in a shooting inside an Indiana laundromat, police said.

A gunman opened fire at a Christian grammar school in California on Wednesday, authorities said.

A gunman opened fire at a Christian grammar school in California on Wednesday, authorities said.

UnitedHealthcare CEO Brian Thompson was shot near a Midtown Manhattan hotel in a potentially targeted shooting early Wednesday, according to police.

The suspect took his own life after firing on children at the elementary school in Palermo, California, on Wednesday, the sheriff said. One of the two injured students was airlifted to the hospital.

The shooting of UnitedHealthcare CEO Brian Thompson appears to be a "brazen, targeted attack," police said.

The masked gunman appeared to be lying in wait and shot Brian Thompson several times from behind, the NYPD commissioner said at a news conference.

The shooting, which appeared to be accidental, unfolded Monday in a parking lot in Rancho Cucamonga, the San Bernardino County Sheriff's Department said.

Brian Thompson was shot and killed outside a Midtown Manhattan hotel Wednesday morning. The alleged killer is on the loose and police believe it may have been a targeted shooting.

A 7-year-old boy fatally shot his 2-year-old brother while sitting in a truck after finding a gun in the glove box, according to authorities in California.

Shots rang out at the Park Plaza Mall in Little Rock, Arkansas, on Black Friday, leaving two people injured, police said.

A police officer has been fatally shot in suburban Chicago after responding to a report of a man leaving a bank with a gun

A 20-year-old mother and her 4-month-old son were shot dead while sitting in their car, in what appears to be a drive-by shooting, according to police.

At least 36 transgender or gender-expansive people were killed in the last year, the majority killed by a gun.

The incidents, which occurred about 45 minutes apart, took place at a parade in the 5th district.

Two people were killed and 11 others were hurt in two shootings that erupted 45 minutes apart near a second line parade in New Orleans on Sunday, authorities said.

Police believe the shooting that pierced a Southwest plane as it prepared for takeoff from Dallas Love Field in Texas was random, sources told ABC affiliate WFAA. 

The president of Tuskegee University in Alabama announced Monday that it was transitioning to a "closed campus" in the wake of a shooting that killed an 18-year-old on Sunday.

The president of Tuskegee University in Alabama announced that the school is being closed to outsiders following a mass shooting.

Jaquez Myrick, 25, was arrested in connection with the deadly shooting at the college campus in Alabama, which killed an 18-year-old and left at least 16 people injured early Sunday.

Jaquez Myrick, 25, was arrested in relation to the deadly homecoming event shooting at Tuskegee University in Alabama on Sunday.

At least one person was killed, and more than a dozen were hurt in a mass shooting at Tuskegee University during a celebration of the school's 100th homecoming.

A North Carolina State student has been arrested for a string of apparently random shootings at cars on multiple highways in Raleigh.

ABC News follows gun violence survivors, Drew Spiegel and Gen Z Congressman Rep. Maxwell Frost, across the country as they push for stricter gun laws ahead of the 2024 presidential election.

Several replica guns have been recovered from the home of a 13-year-old who allegedly planned to scare students at an elementary school.

Authorities are investigating a shooting spree in Raleigh, North Carolina, after at least a dozen cars and homes near Interstate 40 were hit by gunfire. Police say two people have been detained.

ABC News follows gun violence survivor Drew Spiegel and Rep. Maxwell Frost as they push for stricter gun laws.

Local hero Robert “Robbie” Doerr was shot dead in his Indiana driveway on the evening of February 26, 2019. Doerr’s wife, Elizabeth Fox-Doerr remembered being “in panic” at the scene.

"The election of Donald Trump is deeply troubling for our safety and freedom from gun violence," Kris Brown, president of the Brady Campaign to Prevent Gun Violence, said on Wednesday. 

Gun-violence prevention groups said that they plan to double down in their fight for stronger firearm-control laws in the wake of former President Donald Trump's win.

At least two people are dead and six others have been injured in a Halloween night shooting in downtown Orlando, police said.

One man is dead and two others were injured after the gunman fired several rounds, according to police.

A 22-year-old man has been arrested and identified as a suspect in a deadly shooting that erupted on Halloween night in a mall in Vancouver, Washington.

Orlando Mayor Buddy Dyer announced a local state of emergency after two people were killed and several more were injured in a Halloween night shooting.

At least two people are dead and six others have been injured in a Halloween night shooting in downtown Orlando, police said.

Police have not yet said if they are aware of a motive for the double murder.

Atlanta police apprehended an armed individual in Midtown after instructing people to shelter in place Tuesday afternoon due to reports of gunfire near the Four Seasons Hotel.

Police said they are responding to a report of an armed person at the Four Seasons Hotel in Atlanta.

Juliana Magalhaes pleaded guilty to manslaughter for shooting and killing Joseph Ryan in February of 2023.

Gun control activist David Hogg says a “divided Congress” is the biggest obstacle to strengthening gun laws.

Detective Sgt. Monica Mosley, with the Cumberland County Prosecutor's Office in New Jersey, was fatally shot at her home in Bridgeton on Oct. 15, according to police.

A Minneapolis man is charged with attempted murder in the shooting of his neighbor, who had called police about the suspect's threats 19 times in the past year.

Salvador Ramirez, 23, was found with multiple gunshot wounds on Saturday morning, according to Atlanta police.

Attention paid to gun violence prevention has had to compete and, at times, has been overshadowed by other hot-button campaign topics.

From the June presidential debate to the October vice presidential debate, at least 134 people were killed in 149 mass shootings across the United States, according to the Gun Violence Archive.