Authorities in California are investigating the death of a 69-year-old Jewish man, who suffered a fatal head injury during an altercation on Sunday amid dueling pro-Palestinian and pro-Israel demonstrations.

Ventura County Sheriff Jim Fryhoff said in a Tuesday news conference that Paul Kessler got into a physical altercation with one or more counter protesters, "fell backward and struck his head on the ground." The case is being investigated as a homicide and deputies have "not ruled out the possibility of a hate crime," the sheriff said.

Kessler's death comes amid mass protests that've erupted across the globe since the war between Israel and Hamas broke out last month.

The incident in Thousand Oaks, a suburb northwest of Los Angeles, was reported by witnesses as a battery around 3:20 p.m. on Sunday. Police arrived within minutes and found Kessler on the ground, bleeding from his mouth and the back of his head. He was conscious and treated on scene before being taken by ambulance to a nearby hospital.

He died early Monday morning from blunt force head injury and his manner of death was determined to be a homicide, meaning at least one other person was involved in potentially causing Kessler's death, said Dr. Christopher Young, the chief medical examiner in Ventura County, at the news conference.

A unnamed suspect, who was at the demonstration in support of Palestine, stayed at the scene and was interviewed by law enforcement, Fryhoff said. The man was "cooperative" and told detectives he was one of the people who called 911 requesting medical attention for Kessler.

Several witnesses were also interviewed at the scene and "provided conflicting statements about the altercation and who the aggressor was," Fryhoff said, adding that some witnesses were there in support of Palestine and others were there for Israel. Between 75 to 100 people were present at the demonstrations between both groups.

"What exactly transpired prior to Mr. Kessler falling backward isn't crystal clear right now," Fryhoff said. He could not confirm reports that Kessler was struck in the head with a megaphone; however, he did say injuries on the side of Kessler's face "could have been caused by a megaphone."

The man identified as a suspect was temporarily detained on Monday while detectives searched his home. Fryhoff said he could not discuss the search results.

As of Tuesday, no arrests have been made and the investigation remains ongoing, said Fryhoff, who asked that anyone with information come forward or submit videos of the incident anonymously to the sheriff's office.

Fryhoff said, because of the nature of the incident, he is increasing deputy patrols around local mosques and synagogues.

"We understand that the war in Israel and Gaza has led to an increase in hateful and threatening rhetoric and we want to assure the Muslim and Jewish communities that we stand with them both during this difficult time," he said.

'We were in shock'

Lu Johnson told The Ventura County Star, part of the USA TODAY Network, that he saw the protesters around 3 p.m. while he and his son were on their way to buy bubble tea drinks.

On their first pass, Johnson said they saw a man standing by himself on the corner near a Shell gas station holding an Israeli flag. On two other corners they saw demonstrators waving Palestinian flags and carrying signs. After getting their beverages, Johnson and his son drove past the intersection and saw Kessler on the ground.

"We were shock. We saw that man on his back bleeding," Johnson said.

They parked in a nearby shopping center and watched as emergency responders arrived and deputies appeared to be interviewing witnesses. Johnson said after police and ambulances showed up, a pro-Palestinian demonstrator was yelling into a megaphone.

A video of the incident's aftermath shows a pool of blood on the sidewalk and on a cardboard sign near a line of emergency response vehicles. After Kessler was taken into an ambulance, a group of protesters wearing safety vests and holding Palestinian flags remained at the scene, the video shows. One protester chanted into a megaphone, "Stop killing our children now."

Local faith and community leaders react

Ventura County Supervisor Jeff Gorell, said he's "heartbroken" over the death of Kessler, who he said had been "struck at a protest."

"My prayers are with this man's family and friends," he said on X, formerly Twitter. "Our whole community grieves at this senseless loss of life."

Rabbi Michael Barclay of Temple Ner Simcha in Westlake Village, near Thousand Oaks, identified Kessler as Jewish and urged people not to jump to conclusions about his death.

"Please let (law enforcement) do their jobs," he posted on X. "As of right now, there are multiple conflicting witness reports, and no video of what happened before Paul hit the ground. These are good men, and please have faith they will see justice."

He said law enforcement was being cautious before "making accusations," adding: "We need to do the same; and not let this become a spark that starts an inferno."

Omar Ricci, spokesman for the Islamic Center of California in Los Angeles, told the Ventura County Star he didn’t know about Kessler's death but said he condemned any acts of violence.

“There should be no room for any violence here on the home front,” he said. “We can’t allow that to spill over.”

Hussam Ayloush, executive director of the Los Angeles area chapter of the Council on American-Islamic Relations, said in a statement, “We are deeply saddened by this tragic and shocking loss."

Ayloush also urged people to avoid "jumping to conclusions," but extended his caution to prevent people from "sensationalizing such a tragedy for political gains, or spreading rumors that could unnecessarily escalate tensions that are already at an all-time high."

“We urge everyone to wait for the Ventura County Sheriff’s Office to complete its investigation before drawing any conclusions," Ayloush said. "Our thoughts are with the family and the Jewish community during this difficult time."

Contributing: The Ventura County Star; The Associated Press