The 15-year-old was shot in the foot by his younger sibling last night, Joe Silva with the Stockton Police Department said.
Silva said the police are investigating the incident.
The injuries are not life threatening, police said, and the teen has been transported to the hospital.
It is unclear where exactly the shooting happened, as police learned about the incident when the teen showed up at emergency unit just after 8 pm, sacramento.Cbslocal.Com reported.
Police say the gun belongs to the step-dad. The children's parents are cooperating with the investigation, the report said.
The incident comes days after a radicalised couple -- Tashfeen Mailk and Syed Rizwan Farook shot dead 14 people and injured 21 others in San Bernardino in California.
While Farook was a US citizen of Pakistani-origin, Tashfeen was a Pakistani national. Both were later killed by the police in an exchange of fire on Wednesday.
