SANTA MARIA, Calif.—A 20-year-old man tossed an explosive device into the California courthouse where he was about to be arraigned on a gun charge and the explosion left five people with minor injuries and shut down the court complex and other nearby city buildings, police said.

The explosion occurred Wednesday morning in Santa Maria, a city of about 110,000 in California’s central coast region. The suspect ran away after the explosion and was captured as he tried to get into his vehicle parked nearby.

The man, who is from Santa Maria, was wearing body armor underneath his jacket, according to Santa Barbara County Undersheriff Craig Bonner, and was booked on attempted murder and explosives charges. Officials are also investigating whether the suspect is tied to a series of recent arsons.

Officials said it appeared the courthouse attack was related to his earlier arrest on a gun possession charge and not terrorism or an act of political violence.

“We do believe this is a local matter that has been safely resolved and that there are no outstanding community safety concerns,” Bonner said.

The suspect had been arrested last July for illegal gun possession and was to be arraigned Wednesday. When he entered the courthouse and approached the screening station he tossed a bag that then detonated.

Bonner said three of the five victims suffered burns. All were treated and released from a hospital. None were court employees.

Authorities evacuated a five-block radius of businesses, homes, and a school after the explosion. The courthouse will be closed Thursday as police complete their investigation, and filing extensions will be offered for those affected by the shutdown.

Shane Mellon told KSBY-TV that he was at the courthouse when he heard what sounded like chairs falling over.

“It was a loud bang,” he said, adding the bailiff escorted him and others out.

Mellon said he saw what looked like a sweater smoldering and a man screaming while four or five people got on top of him, trying to keep him restrained.

“I think this could have been way worse than it was if not for the deputies just jumping on top of that guy,” Mellon said.

Santa Maria is about 150 miles (240 kilometers) northwest of Los Angeles. The courthouse, which houses state and county courtrooms, was where Michael Jackson was tried and acquitted of sexual abuse two decades ago.