The 15-year-old teen, who cannot be named by police because he is underage, will make his first court appearance in juvenile court Tuesday.
James McLamb, 22, of New Haven, appeared in Stamford court Monday on murder charges and remains in custody on $2 million bond. The bond was set so high because of the "underlying violence of the attack," prosecutor Paul Ferencek said.
Investigators say they expect to make one more arrest in the case.
Antonio Muralles, 52, of Stamford died early Thursday of a stab wound to the chest in the attack Wednesday evening, police said.
He was coming out of the Bedford Street McDonald's Restaurant when he inadvertently spilled coffee on the teen, police said. The teen and McLamb began to verbally attack and then physically attack the man despite his apologies, police said. At some point in the assault, the teen stabbed Muralles, police said.
The teen was part of a group of three to five people who then fled the scene, police said.
Police investigators received a lot of information and video evidence from people who were "sickened" about the attack, Capt. Richard Conklin said at a press conference Monday afternoon.
Police worked around the clock, said Lt. Diedrich Hohn. An important break came when an eyewitness came forward.
"Her information really blew the case wide open," he told the press conference.
Muralles has no children, and his siblings and father live in Guatemala, police said.
His niece, Rosa Reyes, lives in Stamford and she attended the press conference although she did not speak. Later, through an interpreter, she said her uncle loved to sing and play guitar at family get-togethers.
At about 8:15 p.m. Wednesday, Stamford EMS was responding to an unrelated incident when they saw a man collapse at the corner of Broad and Bedford streets outside the McDonald's, police said.
They started to treat the man and saw a stab wound to his chest, police said. He was transported to Stamford Hospital, where he underwent emergency surgery. After several hours of surgery he succumbed to his injuries at 1:07 a.m., police said.
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