The Huntington Beach officers were responding to a disturbance in the neighboring city of Newport Beach around 6:30 p.m. Saturday when the helicopter hit a narrow strip of water between Lido Isle and the Balboa Peninsula.
The National Transportation Safety Board and the Orange County Sheriff's Department are investigating the crash. According to the NTSB, the pilot reported mechanical difficulties and then said the aircraft was going down just a few seconds later.
A full report on the cause of the crash could take upwards of a year to be released.
Surveillance video from a nearby home shows the helicopter making a spiral descent into the water. Witnesses said boaters rushed to pull the officers out of the helicopter, which landed upside down in shallow water.
"We have a lot of helicopters flying around, but this had a higher pitch to it," one witness told Eyewitness News. "It didn't sound right. I looked outside and saw it going in circles."
Nicholas Vella, 44, was identified as the officer who died in the crash, Chief Eric Parra announced during a news conference Saturday night. The 14-year veteran of the Huntington Beach Police Department leaves behind a wife and daughter.
Word of his death drew dozens of officers and first responders, who formed a line outside the hospital to salute his casket as it was escorted by squad cars to the Orange County coroner's office.
Vella "was truly dedicated to his job and was doing what he loved doing," the chief said.
The second officer, who is a 16-year veteran with the department, was taken to the hospital in critical condition but has since been released, according to officials.
It's unclear who was piloting the aircraft at the time of the crash.
The Associated Press contributed to this report.