A 15-year-old boy walking home from school was stabbed to death for his backpack, Southern California authorities said.

Keshawn Brooks was assaulted as the suspect tried to snatch his bag Thursday afternoon outside Stephens Middle School in Long Beach, police said. The suspect ran off.

Brooks, a freshman at nearby Juan Rodriguez Cabrillo High School, was given first aid by witnesses before paramedics arrived. The teen was rushed to a hospital, where he was pronounced dead from serious stab wounds.

After interviewing witnesses, investigators named 18-year-old Giovanny Montelongo as a suspect. He was taken into custody at his Long Beach home on suspicion of murder.

The killing occurred as parents were picking up students at Stephens Middle School, police said. Investigators were asking any witnesses to come forward.

The Long Beach Unified School District was providing grief counselors for students Friday.

It wasn't immediately known if Montelongo has a lawyer.