Officers responded to a call of a shooting in the 400 block of Stoneford Avenue around 5:20 a.m. and found Mejia lying on the ground with multiple gunshot wounds, police said.
He was pronounced dead at the scene.
The 18-year-old's death marks Oakland's 21st homicide this year.
Police said they do not know the motive for the shooting and are asking anyone with information about the crime to contact investigators at (510) 238-3326.
