"California authorities have closed 17 miles of San Diego County beach as they search for a great white shark they believe attacked and killed a man training for a triathlon Friday morning."

"Dave Martin, a 66-year-old retired veterinarian from Solana Beach, was attacked at San Diego County's Tide Beach around 7 a.m., according to the Associated Press. At the time, Martin was swimming with a group that included nine triathletes from the Triathlon Club of San Diego, according to a statement on the Solana Beach city Web site.

"A Solana Beach resident for 38 years, Martin had been with the club for three years and was in the middle of the group when a large shark attacked him 150 yards off shore before vanishing.

"Martin's friends immediately pulled him out of the water and onto the beach."

[ABC News/ AP photo]