aidan fraley , 16 , says his father eric harris ' killer robert bates should never have been allowed to work as a tulsa deputy .
fraley says the police at the scene and those who allowed bates on the streets are to blame but his mother cathy fraley says she forgives bates .
bates has said he mistakenly pulled out a handgun rather than a stun gun when he fatally shot eric harris on april 2 as he lay on the ground .