California military leaders at Camp Pendleton are working to find out how a routine range operation turned deadly.

The military is not releasing the names of the 4-victims until all their families are notified.

They have confirmed the accident happened on a bomb range on base Wednesday.

The military community says it is a tragic reminder that their loved ones are in danger in combat overseas or while training here at home.

"When things like that it’s like a freak accident nobody expects it," said Jenna Erichsen. "We are all here for each other when things like this happen."

No live training exercises were on the schedule Wednesday so it is possible the Marines were killed by an unexploded bomb in the field.