ATLANTA (AP) — The man who fired more than 180 shots with a long gun at the headquarters of the U.S. Centers for Disease Control and Prevention broke into a locked safe to get his father’s weapons and wanted to send a message against COVID-19 vaccines, authorities said Tuesday.

Documents found in a search of the suspect’s home “expressed the shooter’s discontent with the COVID-19 vaccinations,” Georgia Bureau of Investigation Director Chris Hosey said. White had written about wanting make “the public aware of his discontent with the vaccine,” he said.

Patrick Joseph White, 30, also had recently verbalized thoughts of suicide, which led to law enforcement being contacted several weeks before the shooting, Hosey said. He died at the scene Friday of a self-inflicted gunshot wound after killing a police officer.

The suspect’s family was fully cooperating with the investigation, authorities said at the Tuesday news briefing. White had no known criminal history, Hosey said.

Executing a search warrant at White’s home, authorities recovered written documents that are being analyzed, and seized electronic devices that are undergoing a forensic examination, the agency said.

Investigators also recovered a total of five firearms, including a gun that belonged to his father that he used in the attack, Hosey said.

Hosey said the suspect did not have a key to the gun safe, Hosey said. “He broke into it,” he said.

More than 500 shell casings have been recovered from the crime scene, the GBI said.

In the aftermath, officials at the CDC are assessing the security of the campus and making sure they notify officials of any new threats.

The shooting Friday broke about 150 windows across the CDC campus, with bullets piercing “blast-resistant” windows and spattering glass shards into numerous rooms, and pinned many employees down during the barrage. White had been stopped by CDC security guards before driving to a pharmacy across the street, where he opened fire from a sidewalk, authorities said.

U.S. Health Secretary Robert F. Kennedy Jr. toured the CDC campus on Monday, accompanied by Deputy Secretary Jim O’Neill and CDC Director Susan Monarez, according to a health agency statement. Kennedy also visited the DeKalb County Police Department, and later met privately with the slain officer’s wife.

“No one should face violence while working to protect the health of others,” Kennedy said in a statement Saturday. It said top federal health officials are “actively supporting CDC staff.”

He did not speak to the media during his visit Monday. Some unionized CDC employees called for more protections against attack.

Kennedy was a leader in a national anti-vaccine movement before President Donald Trump selected him to oversee federal health agencies, and has made false and misleading statements about the safety and effectiveness of about COVID-19 shots and other vaccines.

Years of false rhetoric about vaccines and public health was bound to “take a toll on people’s mental health,” and “leads to violence,” said Tim Young, a CDC employee who retired in April.