Updated

A male triathlete swimmer was killed Friday morning in a gruesome and violent shark attack at a San Diego County beach.

The victim — one of a group of triathlete swimmers training in the ocean — was pulled into shore, but efforts by medics to revive him failed, Deputy Fire Chief Dismas Abelman told FOX News.

The victim has been identified as Dave Martin, 66, a retired veterinarian who was swimming with members of a triathlon club, said family friend Rob Hill.

Witnesses reported seeing the Martin's leg severed at the knee.

"He had very severe injuries to both legs," Abelman told FOX. He said the wound was a single bite across both legs.

A marine biologist told a beachside news conference Friday that the animal was "almost certainly a great white shark."

"I was told that the victim was pushed up out of the water in a violent attack," said Richard Rosenblatt of the Scripps Institution of Oceanography. "That's typical great white behavior."

Rosenblatt said the bite was likely "clean and massive" and believes the animal was a female.

The victim was swimming with the others when he was attacked at about 7 a.m.

"It looks like the shark came up, bit him, and swam away," said Abelman. A group of about 10 swimmers wearing wetsuits were in the water at the time, he said.

The incident happened at a strip called Tide Beach, about 150 yards offshore. Rescuers took the victim to the nearby Fletcher Cove Park lifeguard station for emergency treatment, but he was pronounced dead at the scene.

A 72-hour advisory closing area beaches was in effect until Monday, said Solana Beach Lifeguard Capt. Craig Miller. The Coast Guard has issued warnings of sharks in the area since the tragic attack. Swimmers were ordered out of the water for a 17-mile stretch around Solano Beach.

The county Sheriff's Department sent helicopters up to scan the waters for the shark. Miller said they'd patrol from the air until about 6 p.m. Friday, and return Saturday and Sunday.

"The shark is still in the area. We're sure of that," Mayor Joe Kellejian said.

Miller said two swimmers were about 20 yards ahead of the man when they heard him scream.

San Diego County sheriff's Lt. Mike McClain said deputies went to Solana Beach shortly before 7:30 a.m. Friday and found a shark-bite victim, who was pronounced dead about an hour later.

Solana Beach is 14 miles northwest of San Diego.

Earlier this year, stories of shark sightings swept the coast from San Diego County north through Orange and Los Angeles counties, The Los Angeles Times reported in late March.

One surfer claimed a bite mark on his surfboard was made by a great white at Bolsa Chica State Beach, but lifeguards at nearby Huntington Beach said there was no evidence of great whites in the vicinity at that time. Other shore authorities also hadn't recorded any unusual sightings.

The last fatal shark attack in California, according to data from the state Department of Fish and Game, took place on Aug. 15, 2004, in Mendocino County at Kibesillah Rock. The victim was a man diving for abalone with a friend.

On Aug. 19, 2003, a woman swimmer was killed by a great white at Avila Beach in San Luis Obispo County on the central California coast. That was the state's first fatal shark attack since 1994, according to the DFG.

The last fatal shark attack in San Diego County was in June 1959, when a free diver was killed, the DFG said.

Overall, shark attacks are extremely rare. There were 71 reported worldwide last year, up from 63 in 2006. Only one attack, in the South Pacific, was fatal, according to the University of Florida.

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The Associated Press contributed to this report.