October 14, 2015 10:57 AM EDT

A San Antonio family visiting San Francisco appears to have captured the moment when a great white shark devoured its prey near Alcatraz, the former prison island, in a cell phone video.

“It’s Jaws!” a boy named Keaton screams with excitement in the clip, as he hums the theme from the hit horror film.

Reports vary on whether the prey was a seal or a sea lion, but marine biologist David McGuire of the group Shark Stewards told CBS San Francisco that it’s not unusual for a shark to eat a sea lion. But it is rare that an attack in the area is caught on camera: “It’s a sign that the bay is getting healthier,” he told the news station. “When you have predations, that means the ecosystem is becoming more balanced.”

Write to Olivia B. Waxman at olivia.waxman@time.com.

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