Deadly California Lightning Storm 'Sounded Like a Sonic Boom'

A rare lightning storm struck packed Venice Beach, Calif., Sunday, killing a 20-year-old man and injuring up to 12 others, one critically, after the same storm had struck a person on Catalina Island.

Firefighters said a bolt of lightning hit the water and the electrical current then traveled, hitting swimmers and surfers.

"The fire department assessed a total of 13 patients, and transported a total of eight patients," Los Angeles Fire Department spokeswoman Katherine Main said.

Lightning Strikes Twice, Kills 2 in Colorado National Park

WATCH: Lightning Strikes Moving Truck

Man's Close Call With Lightning Caught on Video

Five others were injured, but did not require hospitalization, she said.

She said it appears to have been just one powerful lightning strike that hit the shoreline.

"Everyone that had a medical complaint was either in or near the water," Main said.

The man who died was swimming and went missing in the water after the lightning strike, according to ABC station KABC-TV in Los Angeles.

After lifeguards found him in full cardiac arrest, emergency personnel performed CPR and transported him in critical condition to Marina Del Rey Hospital, where he died.

The other person who was critically injured was a surfer, officials said.

Thunderstorms are very uncommon in the Los Angeles area, and people on the beach were shocked by what they experienced. Some said it felt like they got hit over the head with a board and then they were tingling all over.

"It sounded like a sonic boom. It literally shook the buildings," Stuart Archer, who was playing volleyball on the beach, told ABC News. "Shook us on the courts."

He said it was like somebody punched him in the head, his muscles locked up, and he fell.

"I looked up and everybody else was falling over," he said.

Many people who were on the beach said they were knocked down, and lifeguards ran to get victims out of the water.

"Out of nowhere, we heard like a thunderstorm," witness Jason Alas told KABC-TV. "It was like really, really loud."

Before hitting Venice Beach, the thunderstorm moved over Catalina Island where a golfer was injured by lightning.

According to the National Weather Service, before today there had already been 15 lightning strike deaths nationwide this year, including six in Florida.

This was the first death attributed to lightning in California this year.

ABC News' Alex Stone contributed to this report.