Ernest Watkins IV, 14, was arraigned Monday on charges he stabbed a man to death outside the Fields Corner T stop Oct. 6.

A Dorchester District Court judge ordered him held in DYS custody without bail.

Watkins was among a group of several people spotted attacking Cherby LaJoie around 1:15 a.m. on Oct. 6, according to the Suffolk County District Attorney's office. MBTA surveillance footage shows four entered the T stop - one jumping a gate after his CharlieCard wouldn't work - then fled out an emergency exit, the DA's office says.

LaJoie died from multiple stab wounds to the head and chest, the DA's office reports.

Prosecutors say that in addition to a trail of blood, investigators followed tips from witnesses and MBTA CharlieCard records, which led them to somebody who gave them Watkins's name.

According to the DA's office, police went to his Dorchester home Saturday - with a key on a shoestring they'd found near LaJoie's body. The key fit in the front door's lock and worked, police say.

Watkins was then put under arrest, his name to become available under a state law that mandates juveniles be tried in adult court in murder cases.

The DA's office says the investigation is ongoing and that additional people could face charges.