A Jewish man died Monday of injuries sustained during an altercation at a pro-Palestinian demonstration in the Greater Los Angeles area on Sunday, the Ventura County Sheriff’s Office said in a statement. The office, which is investigating the incident, said it has “not ruled out the possibility of a hate crime.”

According to the statement, released Monday evening, Paul Kessler, 69, was suffering from a head injury when sheriff’s deputies arrived at the scene of the protest in Thousand Oaks — a city about 30 miles northwest of downtown Los Angeles — from which several callers had reported the incident.

“Witness accounts indicated that Kessler was involved in a physical altercation with counter-protestor(s),” the department said. “During the altercation, Kessler fell backwards and struck his head on the ground. Kessler was transported to an area hospital for advanced medical treatment” and died from his injuries the next day.

The Ventura County Medical Examiner ruled the cause of death homicide by blunt force head trauma.