One person was dead and three injured near a polling place in California Tuesday evening, when a police-involved shooting caused a recreation center where people were voting to be placed on lockdown.

The gunman — who was heavily armed — was later found dead from either a police or a self-inflicted gunshot would, according to the LA Times.

“We don’t know what the motive is and why this person starting shooting,” the Los Angeles County Sheriff’s Department told the paper.

Officers were met with “gunfire at the scene” in Azusa, California, at around 2 p.m.and voters inside the Memorial Park North Recreation Center were told to stay indoors.

One voter told the network that a “massive shooting is happening and the police have told us to stay indoors. We are currently on locked down.”

There were about 30 people inside the polling station.