Police are investigating the death of a Jewish man in California as a homicide following a clash between pro-Israel and pro-Palestinian demonstrators.
Witnesses told Ventura County police that Paul Kessler, 69, was involved in a dispute with counter-protesters.
"During the altercation, Kessler fell backwards and struck his head on the ground," a police statement said. He died in hospital on Monday.
A suspect has been identified but has so far not been charged or arrested.
Mr Kessler was conscious when he was taken to a hospital on Sunday afternoon, but died of his injuries the next day.
At a news conference on Tuesday, Ventura County Sheriff James Fryoff said that a suspect had "remained willingly and was cooperative" with officers who arrived at the scene.
Police say the suspect claimed that he was among the witnesses who called 911 to request medical attention for Mr Kessler.
The suspect - who has so far not been publicly identified- was later detained and released. A search warrant was also executed at his home in Moorpark, California. Police have said that there may be additional suspects.
Authorities called the incident isolated but said they had not ruled out the possibility of a hate crime.
Mr Fryoff said that witnesses had "provided conflicting statements" and that police were still investigating the events that led to the incident.
"What exactly transpired prior to Mr Kessler falling backwards isn't crystal clear right now," he added.
The Jewish Federation of Greater Los Angeles said that Kessler was hit by a megaphone wielded by a pro-Palestinian protester on Sunday afternoon.
The use of a megaphone has not been confirmed by police, although Mr Fryoff said that "the suspect was advocating for Palestine".
Officials have said that the ruling that the death was a homicide indicates that the death "occurred at the hands of another person" but is not necessarily an indication that a crime has been committed. That determination will be made by prosecutors.
Rabbi Michael Barclay of Temple Ner Simcha, a synagogue close to the altercation, urged for calm until the police were able to complete their investigation.
He said the community should not allow Kessler's death to "become a spark that starts an inferno".
Hussam Ayloush, the executive director of the Los Angeles Council on American-Islamic Relations organisation, called the loss "tragic and shocking".
"We join local Jewish leaders in calling on all individuals to refrain from jumping to conclusions, sensationalising such a tragedy for political gains, or spreading rumours that could unnecessarily escalate tensions that are already at an all-time high," he said.
Kessler's death has occurred during a tense time in the US over the Israel-Hamas war.
Officials have warned of rising threats and religion-based hate crimes against Jewish and Muslim people since Hamas attacked Israel on 7 October.
More than 1,400 people were killed and more than 200 kidnapped, says Israel.
In Israel's retaliatory strikes on Gaza, more than 10,000 people have been killed, according to the Hamas-run health ministry.
More on Israel-Gaza war
Follow live: Latest updates
From Gaza: Stories of those killed in Gaza
History behind the story: The Israel-Palestinian conflict
Christopher Wray, the FBI director, told a Senate panel last week that the terror threat to Americans has been "elevated throughout 2023", but has risen again "to a whole other level" since the war began.
In Ventura County, rising tensions prompted police to increase patrols at mosques, synagogues and community centres.
Benny Gantz and Yair Lapid, senior Israeli lawmakers, also commented on the death, saying it should serve as a warning on the rise of antisemitism.
Demonstrators supporting Israel and those protesting over the rising number of Palestinian deaths have gathered each weekend to support their sides of the conflict.