A 17-year-old freshman at Boston University was struck and killed by an MBTA commuter rail train late Tuesday night as he walked on the tracks near the Massachusetts Turnpike overpass, MBTA Transit Police and the university said.

The student was from China. His name is being withheld until his family is notified, Transit Police Superintendent Richard Sullivan said Wednesday.

“A preliminary investigation suggests that this is a horrendous, tragic accident,’’ Sullivan said. “We as loudly and as frequently as we can try to educate the public on the dangers of trespassing along or on the right of way. This sad event can serve as a tragic reminder that it’s dangerous, and it can be deadly.’’

The student was struck just down the street from his dorm on Buick Street, officials said. Transit Police were notified around 11:40 p.m. that a body was on the tracks, but it was not clear exactly what time the student was struck, or by what train.

The student had to climb a fence to get onto the tracks, officials said. BU students said police do their best to keep young people away, but new students sometimes check them out anyway. Beyond the tracks, the Charles River is visible.

Tuesday was the university’s first day of classes.

“It’s incredibly tragic,’’ said Amira Cohan, a 20-year-old junior who lives in a Buick Street dorm that overlooks the tracks. “I feel for the family. I also lost someone close to me last year. There’s been a lot of death recently. The people that actually knew him, whoever they are, I can’t even imagine.’’

On Wednesday, many students had not heard about the death, and were taken aback by the news.

“It’s so horrible,’’ one student said. “He was so young.’’

A BU spokesman said the school would not release information about the student until his family had been notified.

“The university’s thoughts and prayers are with the student’s family,’’ Kenneth Elmore, associate provost and dean of students, wrote in a Web posting. He urged students to notify their parents that they are unharmed, and outlined support services on campus.

The student’s body was first spotted by the crew of a passing train, who notified the next train coming down the tracks. The conductor of that train also saw the body and stopped, Sullivan said.

The train had 38 passengers on board, according to Keolis spokeswoman Leslie Aun. They had to remain on board until after 2:30 a.m. as homicide detectives investigated.

Police often require passengers to stay on board during scene investigations of fatal pedestrian incidents, Sullivan said.

Boston Police Department spokesman Lieutenant Detective Michael McCarthy said requiring passengers to stay on the train ensures a thorough investigation.

In 2005, two Boston University students were killed by a commuter rail train as they walked on the tracks near Nickerson Field, a short distance from this incident.

Laura Krantz of the Globe staff contributed to this report. Evan Allen can be reached at evan.allen@globe.com. John R. Ellement can be reached at ellement@globe.com.