Michael Aguirre, 26, faces first-degree murder and attempted first-degree murder charges in Quintero's June 2 death and another unrelated shooting.
Police said the girl was approached by three people in the 1700-block of West 48th Street around 6 p.m. when one of them fired shots, striking her in the head.
Neighbors said the girl was leaving a nearby convenience store when she was shot. A bag of snacks lay on the sidewalk as police marked evidence at the scene.
She was taken to Comer Children's Hospital, where she later died.
Detectives processed surveillance video that showed the girl walking with a dog and a young man neighbors identified as her boyfriend. Moments after the two walk out of frame, at least two shots rang out.
SEE MORE: Girl, 14, shot in head after leaving convenience store in Back of the Yards
Another surveillance camera recorded three people dressed in black approaching the intersection where she was shot.
Another video recording showed an SUV waiting for the men in black near an alley as they sprinted toward it, getting in and driving away.
Neighbors said the 14-year-old and her boyfriend were not part of any gang. And witnesses said the girl would often buy snacks at a nearby store, just like she did before being shot.
Aguirre was arrested Monday in Lawndale, police said. He was identified as one of the suspects involved in Quintero's death.
He was also charged in connection with an Aug. 19 incident in which a 21-year-old man was shot in the 10200-block of South State Street, police said.
In late June, a 17-year-old was charged in connection with Quintero's death, as well.
Sun-Times Media contributed to this report.