Two brothers were charged with manslaughter today in the July stabbing of 15-year-old Lance Hartgrove outside the Social Security Administration office in Roxbury, a crime the victim’s mother said grew out of a feud on Facebook.

Rula Jones, 18, and Ilm Jones, 20, both of Mattapan, were arrested Wednesday night and arraigned in Suffolk Superior Court today. They were also charged with assault and battery with a dangerous weapon in the wounding of a second victim during the incident.

The brothers stood in a hallway just outside the courtroom to hide their faces from cameras, before pleading not guilty to all charges. Both men remained in custody on $500,000 cash bail pending a pretrial conference Nov. 8.

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Prosecutor Gretchen Lundgren told clerk magistrate Margaret Sanel that a vicious fight broke out just before 2 p.m. on July 10, after a friend of Hartgrove’s called him to the office at 10 Malcolm X Blvd. when he spotted Rula Jones heading there with his mother and younger siblings.

Hartgrove and Rula Jones had fought at least twice before, Lundgren said.

Hartgrove walked to the office with at least three friends, armed with a kitchen knife, Lundgren said. Hartgrove and his friends argued with Jones, who told Hartgrove to wait for him because had business in the Social Security office, Lundgren said.

Inside the office, Jones’ mother took out a cellphone and called her older son, Ilm Jones, to the scene “to assist,” Lundgren said. Moments later, Hartgrove allegedly threw a glass bottle at the office window, near the spot where Rula Jones was standing inside, and then walked inside with at least two of his friends and started fighting with the teen.

The fight spilled outside. Moments later, Ilm Jones arrived.

One of Hartgrove’s friends was stabbed in the back by a man matching the description of Ilm Jones, Lundgren said. The friend told authorities he then saw Rula Jones stab Hartgrove in the chest, Lundgren said. Hartgrove collapsed and died in a nearby parking lot.

After the arraignment, Hartgrove’s mother, Towanda Kellam, said the defendants’ mother had a chance to diffuse the fight and could have summoned police to the scene rather than call her other son.

“I don’t know what type of mother she is. After what they just read to me saying that she was there when this fight [began] ... me as a mother, I would have stopped it before it started,’’ Kellam said outside the courtroom.

Kellam said the death of her only son grew out of a campaign of harassment that began on the Internet and led to him getting his front teeth knocked out in an assault in February.

Hartgrove was attacked again on May 30 and hit in the mouth with a heavy object, her mother said.

“My son was 15 years old. That was my baby. My son wasn’t a robber,’’ Kellam told the Globe shortly after his death. “He wasn’t a killer. He wasn’t a drug dealer. He didn’t have a criminal record.”