FAIRFIELD (KRON) -- A 15-year old boy is facing assault charges after allegedly stabbing his step-father five times in the back in an effort to protect his mother.

Investigators say the boy witnessed the 29-year old victim hitting his mother several times in the face in an apparent domestic violence case.  Authorities say the teenager picked up a 7" fixed blade knife and stabbed his step-father in the upper back.  

The step-father was taken to NorthBay Medical Center where he is likely to face Felony Domestic Violence charges when he recovers.  The 15-year old was booked into juvenile facilities and charged with Assault with a Deadly Weapon.

Investigators say the step-father has lived with the boy's mother for nine years but the alleged stabber is a child from a previous marriage.

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