"It was very, very quick," Assistant District Attorney Carolyn Naylor said, adding that Carlyle was among a group of teens hanging out near a corner store when Sanabria opened fire after exchanging words with Carlyle as he walked by.
In Pennsylvania, all murder suspects, regardless of their age, background or role in the crime, are charged as adults, and a conviction for first- and second-degree murder carries an automatic minimum sentence of life-without-parole.
Consequently, Pennsylvania leads the nation - and the world - in the number of juveniles it condemns to prison for life, incarcerating a fifth of about 2,500 juvenile lifers nationwide.
But last June, the U.S. Supreme Court declared that penalty unconstitutional for minors, forbidding it as a mandatory sentence. The justices also suggested it be used rarely and only after judges consider cases individually, weighing an offender's age, intellect, background and role in a crime.
Sanabria is the third Philadelphia juvenile convicted of murder since the federal ruling. But the other two - Mikechel Brooker and Ferock Smith, convicted of killing competing drug dealer Barry Jacobs Jr. in July 2008 - dodged life sentences and instead got minimum sentences of 35 and 50 years, said Naylor, who also prosecuted them.
Naylor called Sanabria's sentence appropriate, because he was on probation for a simple-assault conviction and wanted on a bench warrant when he killed Carlyle.
But attorney Bradley Bridge, who has argued on behalf of juvenile lifers before the state Supreme Court, said Sanabria's sentence "is inconsistent with the Supreme Court's ruling ... and is of questionable constitutional validity."
"The United States Supreme Court said that it should be the very rare or unusual case that merits a sentence of life without parole (for juveniles). This is not such an unusual case, and similarly, I would expect that on appeal, there will be a challenge," Bridge said.
Thomas L. McGill Jr., Sanabria's defense attorney, couldn't be reached for comment.