Integrated Homicide Investigation Team Sgt. Bari Emam says the youth was arrested shortly after the Tuesday night incident.
He was expected to be formally charged Thursday with aggravated assault and assault with a weapon.
Emam says robbery appears to be the motive.
He says there's no indication that the victim and attacker knew each other.
The name of the 19-year-old victim is not being released at this point and the 16-year-old suspect can't be identified under provisions of the Youth Criminal Justice Act.