"This kid was doing everything right in his life and he wound up being shot," one law enforcement source said.
Devine's killing was the city's last of 2013. Including Devine, 247 people were killed in Philadelphia this year - the lowest annual homicide total since 1967, and a 25 percent drop from last year's total.
The young man's death left students at his high school reeling, principal Greg Hailey said.
Devine, a member of the basketball team, was to have graduated this year, Hailey said. He described Devine as a quiet student, well liked and courteous.
"He never had a bad word to say about anyone," Hailey said. His teammates, the principal said, are "taking it pretty hard."
The team planned to play a scheduled game Thursday in Devine's honor.
"They want to play and dedicate their season to Quahdir," Hailey said. "They want to honor his memory today and at every game they can."
The school community is also organizing a collection for Devine's family, and grief counselors were on hand Thursday to help students, Hailey said.
Law enforcement sources say Devine was walking home from a party with two others on New Year's Eve when he stopped at the BP gas station near Sixth Street and Girard.
He and two others crossed Girard and were walking south on Marshall Street when a white car approached them. The group ran - from gunshots, police believe.
A witness told police that a member of Devine's group pulled a gun, fired at the car, and fled. As the group ran, Devine fell to the ground, law enforcement sources said. A friend bent over him and yelled, "Get back here - what did you do to my friend?" according to law enforcement sources.
Police are still unsure who fired the shot that killed Devine.
The friend then ran to a security guard at a nearby store and asked him to call police. Within moments, a group of people had crowded around Devine, some taking video with their phones of the 18-year-old lying shot in the street.
Anyone with information on Devine's killing is being asked to call homicide detectives at 215-686-3334 or 215-686-3335.