SAN FRANCISCO - A man who was stabbed to death aboard a San Francisco Bay Area commuter train Tuesday may have been trying to stop the theft of another rider's shoes, authorities said.

The man was stabbed around 1 p.m. aboard a BART train pulling into a Hayward station.

Police were looking into whether the victim, a man in his 40s, was a good Samaritan who tried to stop the suspect from stealing items from another person, possibly shoes, the San Francisco Chronicle reported.

The suspect ran from the station. He was arrested a block away after employees of a car dealership said he tried to steal a van, the Chronicle said.

Steve Castro, an employee at Elias Motors, said he was showing a customer the van when a shirtless man snatched the keys from his hand.

The two fought and at one point the man tried to open the van doors.

Castro told the paper that the man eventually asked him to stop, telling Castro: “You're going to kill me.”

“I told him, `Give me the keys, and I'll let you go,”' Castro said.

The man walked across the street toward a bus stop and was arrested by transit officers searching for the suspect.

“This is something that's very tragic. It's rare on BART,” BART Police Chief Ed Alvarez said. “I do want to assure our ridership that BART is safe and we're continuing to reassure them by providing a presence in our system.”

BART will increase the presence of police officers, community service officers and fare inspectors at station platforms, said Robert Powers, the agency's general manager.

“We are heartbroken that a person has lost his life due to violence on one of our trains this afternoon,” he said in a statement.

The stabbing follows the high-profile death in July of 18-year-old Nia Wilson, who was stabbed in an unprovoked attack on her and her sister in an Oakland BART station.

John Cowell, a 27-year-old parolee, was found competent to stand trial but his case is in legal limbo. A judge in October agreed to seal a motion by Cowell's attorney to dismiss the case.

The family of Wilson claims BART failed in its duty to ensure its customers are safe and that BART has failed to sufficiently address crime on its transit lines.