A college student has been shot to death at a popular tourist attraction in San Francisco.

Authorities say 20-year-old Calvin Riley was shot in the chest Saturday night by an unknown assailant at Aquatic Park near Ghiradelli Square. He was pronounced dead at the scene.

The U.S. Park police and local homicide detectives are investigating what led to the shooting.

National Park Service spokesman Lynn Cullivan says investigators believe there are witnesses to the attack because it happened at a bustling tourist destination in the Fisherman's Wharf area. They are seeking tips.

Riley was set to pitch baseball in his second year at San Joaquin Delta College Mustangs in Stockton.

A relative who set up a fundraising website to help pay for Riley's funeral couldn't be reached for comment.