A 16-year-old Roxbury youth was held on half a million dollars’ cash bail for allegedly stabbing an adult on an MBTA bus this week and had his open bail on two pending cases revoked, Suffolk County District Attorney Daniel F. Conley said today.

The defendant, whose name is not being released because he is a juvenile, was arraigned in the Boston Juvenile Court this morning on charges of armed assault with intent to murder and assault and battery with a dangerous weapon. The youth was arrested yesterday afternoon by MBTA Transit Police investigating the Tuesday evening incident onboard a Route 23 bus.

“From what we’ve gathered thus far, this was a vicious and utterly pointless attack,” Conley said.

In addition to setting high bail, Judge Paul Lewis revoked the teen’s open bail on an open drug case and an open assault case.

The victim, a 47-year-old Dorchester man, suffered multiple stab wounds during the incident, which took place at about 6:20 p.m. as the bus traveled on Ruggles Street. The suspect, whose visage was captured by multiple surveillance cameras, then fled the bus in the direction of the Whittier Street Housing Development.

The youth was identified and apprehended after Transit Police publicized the surveillance imagery and shared it with other local law enforcement agencies.

The juvenile was represented today by attorney Walter Landergan. He will return to court on Sept. 16.