Two young men and a juvenile were arraigned yesterday in West Roxbury Court on charges that they tackled a Jamaica Plain woman Tuesday night and were allegedly trying to steal her backpack when an unknown man confronted the assailants, scaring them away, Suffolk County District Attorney Daniel F. Conley said.

At their district court arraignment, YAHYA AHMED, 18 (D.O.B. 1/1/91), of Jamaica Plain, and ATIF MOHAMMED 18 (D.O.B. 1/1/91), of Brighton were each charged with assault and battery and assault with intent to rob for their role in the Dec. 22 incident.

Assistant District Attorney Mark Swadling requested that each be held on $5,000 cash bail. District Court Judge Kathleen Coffey imposed a $500 bail on Ahmed, and released Mohammed on personal recognizance. The judge also ordered both to have no contact with the victim.

The 16-YEAR-OLD JUVENILE was also charged with assault and battery and assault with intent to rob in the Juvenile Session at the West Roxbury District Court. Swadling recommended that the juvenile be held on $1,000 cash bail. In lieu of monetary bail, a clerk magistrate released the juvenile to his parents, imposed a 5 p.m. curfew, and ordered him to stay away from the victim and his co-defendants.

“We can only imagine what could have happened to this woman if this unknown Good Samaritan had not intervened,” Conley said. “We thank him for his help, and only wish that we knew his identity so that he could be recognized for his kindness.”

At about 7 p.m. Tuesday night, Boston Police officers received a 911 call from a woman reporting that she had been the victim of an attack and attempted robbery at the corner of Boylston and Germania Streets in Jamaica Plain.

Evidence suggests that the victim was walking on Boylston Street when she was suddenly attacked. One of the defendants allegedly jumped on her back, knocked her to the ground and attempted to take her backpack. As the victim struggled with her assailant – later identified as Mohammed – she was dragged into the street, as the other defendants stood around her.

A man driving down Boylston Street in a black car stopped his car, got out and started to yell at the woman’s assailants, scaring them off. That man was able to locate a Boston Police officer who was doing a foot patrol nearby. The witness told the police officer that he saw a woman being “robbed” and “dragged” by three teenage males on Boylston Street, and proceeded to give that officer their description.

Within minutes, responding officers were able to locate three teenage males matching the witness’s description standing in front of a store at 1890 Columbus Ave. The victim was brought to the scene, where she positively identified the three males as her assailants and the men were arrested.

Ahmed was represented by attorney Jane Petkin, and Mohammed was represented by attorney Fran Tucker. Both are expected to return to court on Jan. 14, 2010. The juvenile was represented by attorney Frank Michaelson, and is expected to return to court on Jan. 15.