BOSTON (CBS) – One man is dead and another wounded in a stabbing on an MBTA bus in Roxbury.

The victims were stabbed in the number 44 bus near 135 Humbolt Avenue, outside the Trotter Elementary School at around 9 a.m.

WBZ-TV reports both men are in their 20s.

The school is in “safe mode” as a precaution while police search for four suspects seen running from the bus.

It is unclear how many people were on the bus at the time, or if any students were on the bus.

The victims were both taken to Boston Medical Center where one was pronounced dead. The second victim has non-life threatening injuries.

Their names have not been released at this point.

Police tell WBZ News Radio both victims have known gang affiliations and are looking into whether that is connected to the incident.