A 20-year-old man was shot and killed while playing Pokemon Go near San Francisco’s Fisherman’s Wharf, authorities said Sunday.

The shooting of Calvin Riley occurred about 10 p.m. Saturday in Aquatic Park, said Sgt. Robert Jansing, a detective with the U.S. Park Police. Aquatic Park is adjacent to Ghirardelli Square in San Francisco Maritime National Historic Park.

Riley was walking on the promenade along the water and playing the popular cellphone game when he was gunned down. The assailant did not take any of Riley’s property or attempt to rob him, Jansing said.

Investigators were puzzled by what led to the slaying.

“There doesn’t appear to be any outstanding motive right now,” Jansing said.

Although the shooting occurred late at night, several people were still at the park, which annually sees about 4 million visitors, said Lynn Cullivan, a park spokesman.

Still, Jansing said no witnesses are believed to have seen the gunman. Investigators are collecting footage from surveillance cameras in the area, which may reveal the shooter’s identity.

Riley hailed from San Mateo, Calif., where he graduated from Junipero Serra High School in 2015. At San Joaquin Delta College in Stockton, Riley was studying kinesiology and playing on the college’s baseball team, according to the school website.

On a fundraising website set up for Riley’s funeral expenses, his cousin Gabriel Morales wrote that the family learned early Sunday morning that Riley had died.

It’s unclear if the shooting was related to Pokemon Go, which has surged in popularity since it was released this summer.

The app uses players’ smartphone cameras and GPS technology to guide them to real locations to “collect” Pokemon, or “pocket monsters.” Players point the camera and virtual characters appear against the real-world backdrop. Then players toss a virtual ball to capture that character.