Cellphone video showing a great white shark killing a sea lion was the first time when a great white shark was caught attacking and killing another creature in San Francisco Bay, just off Alcatraz.

As per officials, the event took place on October 10, and was filmed by visitors to the island. One can see a large patch of blood in the water, and a great white shark surfacing to eat a chunk of what appears to be sea lion flesh.

David McGuire, director of the San Francisco-based shark conservation group Shark Stewards, said in a statement that this is the first time they recorded predation in the San Francisco Bay.

"It definitely looks like a white shark, about 8 to 10 feet [long], from the phone video sent to us. The tourists were pretty excited", he said.

Several great white sharks tagged by researchers have been recorded entering waters of the bay in the last few years, said officials. They said that five animals ventured into the bay in 2007 to 2008. But this is the first record of one attacking and feeding on a large marine mammal.

There are so far no latest records of a shark attack on a human in the bay. In May 1959, an 18-year-old named Albert Kogler Jr. died after being attacked by a shark while swimming off of San Francisco's Baker Beach. The video was posted on YouTube.

"Everybody have a camera now," he said. "He cannot escape anymore .everybody can see you."

"Lifeguards will post if there's a sign," said McGuire. "And look at nature. Look at the circling of birds, if there's a lot of activity under the water, if seals are swimming away quickly you should probably get out of the water because there's may be a shark preying."