Authorities have filed felony charges against a man arrested this week at Kaiser Permanente Medical Center in Downey after police officers responding to a report of gunfire—prompting a lockdown and evacuation even though police later determined no shots had actually been fired.

Jesus Rafael Chavez, 33, of Lynwood, pleaded not guilty Thursday to one count of vandalism with over $400 damage and two counts of having a concealed firearm, along with a handgun allegation.

Chavez—who could face up to four years in state prison if convicted as charged—was ordered to be held in lieu of $100,000 bail while awaiting his next court hearing Sept. 25.

Chavez allegedly was causing a disturbance inside a medical building when a security officer contacted him Tuesday, authorities said.

“One of the Kaiser security personnel went over and contacted him, at which time he threw a chair through a window and produced a handgun,” Downey Police Chief Carl Charles told reporters later that day. “He broke a window with the chair.”

Police were initially called at 11:34 a.m. that day to respond to a disturbance that was reported inside one of the Kaiser Permanente medical buildings at 9333 Imperial Highway. Officers subsequently received reports about a possible active shooter, according to a statement issued by Downey police.

Police located Chavez, who surrendered without incident around 12:30 p.m. outside the building and was unarmed when he was taken into custody, according to the police chief.

He had allegedly been armed with a handgun that was recovered at the scene, but detectives determined that no shots were fired inside the building, according to Downey police.

Police said 400 people were evacuated from the building.

No one was injured, according to the police chief, who said a systematic search was done to ensure that there was only one suspect.

Charles noted that active shooter training had recently been done at the facility.

Kaiser Permanente issued a statement saying the disturbance occurred in the Orchard Medical Building at the hospital campus, and the facility was locked down during the investigation. Shortly after 5 p.m., Kaiser officials said the “hospital, emergency and urgent care departments and most of the Orchard Medical Office Building” had reopened.

“We are working to reschedule all missed appointments that were canceled due to this incident,” according to Kaiser. “The safety of our patients, employees and physicians are paramount, and we’re grateful there were no injuries.

“We recognize the stress that can be brought on by a situation like this and are offering behavioral health services onsite to (Kaiser) members, employees and physicians.”