The teen, identified by family as Iran Moreno-Balvaneda, was in his bedroom playing video games when he was shot.
The shooting happened Saturday just after 6 p.m. in the 900 block of North Raymond Avenue. Police say several shots were fired in the area when a single bullet entered a window of a home, striking the teen.
First responders arrived within a minute of the family's call for help. They performed CPR and transported him to a local hospital, where he was declared dead.
"He is a straight A student. He spends all his time inside his room, with his family, and today is not there," said Pasadena Police Chief John E. Perez.
Perez says there has been an increase in gang activity and shootings in the city, despite stepped up patrols. Neither the teen or family was the intended target of the bullet.
"We don't know who did this yet, but we will. We will catch these criminals and we will catch them quick," he added.
The Pasadena Police Department is asking the public to come forward with any information.
"If you know anything about this tragic incident, or you saw anything, please, please, please come forward to the Pasadena Police Department," said police Cmdr. Mark Goodman. "We will keep your information anonymous. What we want to do is find the people who are responsible for this tragic incident and bring them to justice."
A GoFundMe account has been set up.