The incident happened just before 9:30 p.m. Thursday at the store near Chatsworth Street and Zelzah Avenue.
According to the Los Angeles Police Department's Devonshire Station, a group of young people were hanging out after a football game at Granada Hills Charter High School.
It's unclear what sparked the shooting but at some point, the 17-year-old was shot on his left leg just above the knee. It's also unclear if the boy is a student at Granada Hills Charter or another school.
Police said he ran inside the Ralphs store and was later rushed to the hospital. The teen is expected to be OK.
AIR7 was above the scene as the investigation was unfolding and captured the teen being placed in an ambulance. There was also a trail of blood leading into the store.
Meanwhile, many students who attended the football game were shocked to hear about the shooting.
Some parents told Eyewitnesses News they were notified Thursday night about what took place. They shared an email from the school's administrative director, Julia Howelman, who said it appears that students from Granada Hills Charter as well as other school were involved in the incident.
"The well-being of our students is paramount. We are offering counseling services and support to any students who may feel distressed by this event."
Parents were left with differing opinions on whether or not to let their children attend late night school events moving forward.
"I don't want to restrict my daughter having fun because I never had that experience," one parent said. "There's always police here. That's the good thing about it. I love their school, their security is good."
Information regarding suspect(s) was not immediately available. Anybody with information is asked to call LAPD's Devonshire Division.