Why am i getting theese sick thoughts about killing my dad?

my dad has put my mum threw alot hes caused my family alot of trouble and im sick and tired of it, he has beaten me up pushed me down the staris we do alot for him but he throws it back in are faces. hes diabtes tpye 1 and he takes insulin needles however am getting theese thoughts in my head to double his dosage up to kill him. im aslo getting thoughts to get a knife and slice his throat. and other things im 16 btw. what do you think i should do is this normal? am i just upset and angry?