Ransome's brother Jerry, 23, and Sean Gordine, 22, were each sentenced to 40 years to life on their second-degree murder convictions.
Both benefited from last year's U.S. Supreme Court decision that life sentences without parole were unconstitutional for murder defendants under 18, which they were at the time of the killing. They could be paroled after 40 years.
A fourth man convicted of second-degree murder, Eric I. Gales, 23, will be sentenced Sept. 13.
According to Assistant District Attorneys Mark Gilson and Andrew Notaristefano, the four, members of a gang called the Parkside Pushers, watched Thierry talking to three friends, decided they had money, and moved to rob them.
The four armed men confronted Thierry and his friends, and Thierry ran, prosecutors said. The robbers opened fire and Thierry was shot in the back of the head.
The volatile hearing was interrupted as Lerner sentenced Gordine.
Gordine's brother Domonic, 23, who is deaf, was seated in the second row of the gallery, behind several of Thierry's friends and relatives. As Gordine's sign-language interpreter relayed the sentence, Gordine cried out and stood.
"He punched me in the head," cried out Jaimey Vona, a lifetime friend of the victim.
Tracy Simmons, a victim-family counselor with the District Attorney's Office who was seated next to Thierry's mother, Lorraine, also stood, shaken, and felt her back. Neither woman was seriously injured.
Detectives and sheriff's deputies quickly wrestled Domonic Gordine to the floor and cuffed him. Officials said he would be charged with two counts of simple assault.
The incident delayed the hearing for about 30 minutes while investigators tried to sort out what happened.
Vona said Domonic Gordine struck her in the head. As his fist went past the side of her head, she said, a bracelet flew off his arm and hit Simmons in the back.
Others said they thought Gordine was trying to throw the bracelet at the judge and accidentally hit the women.
Gordine's mother, Shavell, said the incident was an accident that coincided with her son's emotional outburst.
She said she was angry because her son was taken into custody without a sign-language interpreter and would not understand: "He's being arrested without getting his rights."
During sentencing, Thierry's mother made an emotional and at times vitriolic statement about the impact of the death of her only child.
She said Michael was a star baseball player at George Washington High School and was 10 days away from completing his apprenticeship with Electricians Local 98.
"He was the best, he had it all until he crossed the paths of these animals," Thierry said. "I never hated or despised anyone in my life until the likes of you. . . . I hope you burn in hell."
Patricia McDonald, mother of slain Philadelphia Police Sgt. Patrick McDonald, who was a friend of Thierry's, read aloud a victim-impact letter her son composed before he was shot to death in the line of duty in 2008.
All three men apologized at length to Thierry's family and friends.
Gordine sobbed as he told Lerner, "I didn't mean for no one to be killed. I didn't want no one to die."
Contact Joseph A. Slobodzian at 215-854-2985, firstname.lastname@example.org, or follow @joeslobo on Twitter.