SAN FRANCISCO (AP) — A man flashed a gun several times on a crowded commuter train in San Francisco, but passengers were so absorbed in their phones and tablets they didn’t notice until he randomly shot a university student, investigators said.

Security video footage showed the gunman pull out the .45-caliber pistol, raise it and point it across the aisle before putting it back against his side, authorities told the San Francisco Chronicle (http://bit.ly/1crPYQc ) in a story Monday.

The man drew it out several more times and once wiped his nose with the hand holding the gun, the newspaper reported. Prosecutors have said he was looking for a victim.

“These weren’t concealed movements — the gun is very clear,” said District Attorney George Gascon. “These people are in very close proximity with him, and nobody sees this. They’re just so engrossed, texting and reading and whatnot. They’re completely oblivious of their surroundings.”

Nikhom Thephakaysone, 30, is accused of fatally shooting Justin Valdez, 20, in the back of the head as Valdez exited the train on Sept. 23. Thephakaysone has pleaded not guilty to murder and other charges.

San Francisco police officials say people who pay too much attention to digital technology are also vulnerable to theft.

“Oftentimes when you interview people who get their phones stolen, when you ask them to describe where the person came from, what he was wearing, they have no idea,” said San Francisco police Chief Greg Suhr.