The person who died when a boat sunk in the frigid waters near Alcatraz in the San Francisco Bay on Tuesday has been identified.

Clifford Joseph Boisa, 79 of Sutter County, died when the pleasure boat carrying 20 passengers capsized near the former prison.

Three of the passengers still remain missing while the rest were rescued. A dog was also found dead.

The passengers were members of an extended family gathered for a memorial service that included spreading ashes for a loved one in the San Francisco Bay, the New York Times reported.

It remains unclear what caused the boat to sink. Windy conditions on the Bay during the summer can create hazards for boating, authorities have said.

The vessel was roughly 600 yards off Alcatraz between the island and the Golden Gate Bridge when it started sinking Tuesday afternoon.

The US Coast Guard initially classified the emergency as a “vessel fire” and said 19 people were aboard when the sinking began. But the San Francisco Fire Department said during a 5 p.m. news conference that crews found no evidence a fire had occurred.

Fire officials described the boat as a three-level cruiser vessel that was already mostly underwater when rescuers arrived, with only the top deck still visible above the surface. When crews arrived some people were in the water while some were on the boat.

Officials said the boat launched somewhere near San Francisco’s St. Francis Yacht Club.

Commercial fishermen Mike Montoya and Justin Marceline recalled victims banging on windows and trying to stay alive as they pulled them from the water.

“There was even people banging at the windows as they were like filing out, and as soon as people were hitting the water, we were just trying to pick them up as fast as we can,” they told NBC Bay Area. “Some people didn’t even have life vests on and they were drowning.”

The Coast Guard and San Francisco Fire Department are still searching for the three individuals, and they’re using “thermal imaging, tide prediction, and modeling to help direct search efforts.”

Download The California Post App, follow us on social, and subscribe to our newsletters