The officer of the Federal Protective Service fired a weapon during the rally at the Federal Building in Westwood, according to a sheriff’s statement. The FPS is the security police division of the Department of Homeland Security.
The demonstration, which drew several hundred people, was breaking up when pro-Israel and pro-Palestinian supporters began to clash.
Witnesses said the confrontation included a scuffle between the pro-Israel protesters and men who drove past the protest in a truck displaying a Palestinian flag, KNBC-TV reported.
A man in the truck said the Palestinian flag was ripped away. When the truck’s occupants attempted to retrieve the flag, there was a struggle, witnesses said.
The officer sought to intervene and fired once, the sheriff’s statement said. There were no injuries.
Four people were arrested, officials said.
The shooting will be investigated by the Sheriff’s Department, assisted by the FBI, bureau spokeswoman Laura Eimiller told KNBC-TV.
Sunday’s rally followed a similar one Saturday in support of Palestinians.