A 19-year-old Santa Rosa man was struck by a SMART train Thursday in northwest Santa Rosa while riding his bike across the train tracks, the first accident involving the commuter rail system since it opened two months ago.

The man, whose name was withheld, was taken to Santa Rosa Memorial Hospital with injuries that did not appear to be immediately life-threatening, the Santa Rosa Police Department said in a news release.

The man was riding his bike east on a West Steele Lane sidewalk as the southbound train approached, lowering the gate at the rail crossing and activating warning bells and lights, said Lynnette Cowsert, who witnessed the 3:55 p.m. accident.

“The (gates) were down, and I thought he was going to stop,” said Cowsert, who was stopped at the crossing. “Ding, ding, ding, and I hear the train. And the next thing I see is him rolling under the train, and his bicycle is under the front of the train.”

The man was wearing earphones and talking on his cellphone, and apparently did not notice the oncoming train or the lowered gates, police said in a statement. He was thrown 20 to 30 feet across West Steele Lane, police said. His bicycle was lodged under the right front train wheel.

Cowsert said the cyclist did not appear to be wearing a helmet.

“You see that, and you’re just like, ‘Oh my God,’” she said. “I’ve just kept thinking it’s a matter of time because I see people stop on the tracks. I thought for sure this guy on the bike, that he saw the crossing guard down and making noise and flashing, but maybe he didn’t.”

The accident is the first since the Sonoma-Marin Area Transit system launched regular service Aug. 25, said Jeanne Mariani-Belding, spokeswoman for SMART.

“I think the most important message here is, safety really is our top priority,” Mariani-Belding said. “We really are asking people to please be alert and aware near all tracks and trains and avoid distractions.”

You can reach Staff Writer Christi Warren at 707-521-5205 or christi.warren@pressdemocrat.com. On Twitter @SeaWarren.