PHILADELPHIA (CBS) — The FBI told CBS News the AR-style rifle used by the shooter in the attempted assassination of former President Donald Trump was legally purchased by and registered to the shooter’s father.  

Gun legislation is both complex and controversial and the laws change from state to state. Assault rifles, like the one used to shoot Trump, are banned in nine states, including New Jersey and Delaware.

“This is just a fact here in Pennsylvania, and in many states, those rifles are legal to buy,” Josh Fleitman, the campaign director with CeaseFire PA, said. “They were federally banned for 10 years, and once that ban was allowed to expire, we saw the rate of mass shootings triple.”

CeaseFire PA is a nonprofit, non-partisan gun violence prevention organization. The group has long been calling for the state to close a background check loophole for long guns including automatic rifles. Currently, Pennsylvania requires background checks for all handgun sales. It also requires background checks for long guns like assault rifles purchased from a firearm dealer but not those purchased from a private seller.

“Maybe it’s your next-door neighbor, maybe it’s the stranger in the parking lot outside of a gun show — if you’re buying an AR-15 or long gun from them, there’s no background check required,” Fleitman said.

AR-style rifles have been the focus of debate for the last two decades because it’s a weapon commonly used by mass shooters. The sheer velocity at which the bullet exits the gun is much more catastrophic to the human body compared to a handgun.

The Giffords Law Center tracks the correlation between gun laws and gun violence across the United States and gives states a grade on their prevention efforts. The group gives New Jersey an A, Delaware a B+ and Pennsylvania a B, recommending Pennsylvania close the background check loophole, pass a red flag law that prevents a person who might be dangerous or in crisis from having a gun, and enact a safe storage law.

Residents in Pennsylvania react to Trump rally gunman being from Bethel Park

The Pennsylvania State Police released the names of the three attendees shot during the attempted assassination of former President Trump at Saturday’s rally in Butler County.

The deceased victim was identified as Corey Comperatore, 50, of Sarver, Pennsylvania.

The second victim was identified as 57-year-old David Dutch of New Kensington, Pennsylvania, who is listed in stable condition. The third victim was identified as 74-year-old James Copenhaver of Moon Township, Pennsylvania; he is also listed in stable condition.

“I am sure everyone has seen the news and are appalled at how divided we have become. Well, it has finally hit home to the League. It is with great sadness that I report that one of the civilians shot at the rally was one of our own,” Matt Popovich, District 8 vice commandant of the Marine Corps League of Pennsylvania Inc. wrote in a post on Facebook.

TRUMP’S SURVIVAL WAS ‘MIRACULOUS’ GIVEN BULLET’S PROXIMITY TO HIS BRAIN, DOCTOR SAYS

“Commandant David Dutch of Westmoreland County is in critical condition. He was shot in the liver and chest. He has had one surgery and is undergoing another this morning. He is currently in an induced coma. Please keep him and his family in your prayers,” Popovich continued.

TRUMP RALLY VICTIM IDENTIFIED AS COREY COMPERATORE, ‘HERO’ SHIELDED WIFE AND GIRLS FROM BULLETS

When Fox News Digital reached out to the Marine Corps League of Pennsylvania Inc., they declined to comment. 

Blood is seen in the stands after shots were fired at Republican presidential candidate Donald Trump at a campaign event in Butler, Pennsylvania, on July 13, 2024. (Rebecca Droke/AFP via Getty Images)

“These victims and their families are certainly in our thoughts today,” said Col. Christopher Paris, Pennsylvania State Police commissioner. “The Pennsylvania State Police continue to work tirelessly alongside our federal, state and local partners as this investigation continues.”

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Supporters are seen covered with blood in the stands after shots were fired at Republican presidential candidate Donald Trump at a campaign event in Butler, Pennsylvania, on July 13, 2024. (Rebecca Droke/AFP via Getty Images)

Pennsylvania Gov. Josh Shapiro ordered U.S. and state flags on all state facilities, public buildings and grounds to fly at half-staff in Comperatore’s honor.

Comperatore, 50, was a former fire chief for Buffalo Township, a volunteer fire service, local news station WPXI reported.

Shapiro said on Sunday he spoke with Comperatore’s wife, who noted that he was a man of faith.

“We lost a fellow Pennsylvanian last night,” Shapiro said at a news conference. “Corey Comperatore was a girl dad. Corey was a firefighter. Corey went to church every Sunday. Corey loved his community, and most especially, Corey loved his family. Corey was an avid supporter of the former president and was so excited to be there last night with him in the community.”

During Sunday’s press conference, Shapiro called on Americans to come together in prayer and to retreat from hate and malice. 

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“This is a moment where all of us have a responsibility to take down the temperature, rise above the hateful rhetoric that exists, and search for a better, brighter future for this nation. I ask that you join Lori and me in prayer for the two Pennsylvanians still in critical condition, for the family of Corey Comperatore, and for former President Donald Trump,” Shapiro said.

The FBI is investigating the shooting as an assassination attempt.

Fox News Digital’s Michael Dorgan and Chris Pandolfo contributed to this report.