My son is 8 years old and at least twice a day he becomes very mean and verbally abusive. He says he is going to kill himself and other members of the family, usually me. I have tried being very nice and telling him that is unacceptable. I have taken away some of his favorite things, computer games, etc. And I have actually spanked him. Although this has only happened twice. He is a perfect angel at school.
This morning he grabbed a pair of scissors and said he was going to kill me in my sleep tonight.
My question is what should be my next step. Can't do this much longer.

Visit to the psychologist?

I think it is time to maybe not try being so nice. It seems clear that he has no respect for you. I would say he doesn't have a mental issue since he is fine when he is not with you so it seems like it is more directed at you. He gets angry, knows you are a pushover, and he runs with it...he knows he can threaten you, he knows he can disrespect you. Maybe try showing him that you, the parent, are in control and not him.

Limit his TV viewing; or monitor what he watches. Sounds to me that he is watching horror movies. There are additives to put on your TV that will monitor for you.

How does the rest of the family act? Is there violence between family members? Do other people have angry outbursts? Yell and scream? Insult each other?

What is he like at school? What has the teacher told you? I'd call my pediatrician and get an appointment right away. Hopefully, you will receive a referral to a good psychiatrist or psychologist.

I agree with TJ, I'd talk to his teacher, and then book an appointment with your doctor, go from there.

Children can get upset and have tantrums, they all do. But it's not normal for a child to threaten their parents or family members with scissors, or threaten to kill them. Either he's learned this somewhere, there's a lot of violence in the home and he's emulating it, or there's something else going on in his head that you can't understand or see in or order to fix.

I agree with everyone else, talk to his teacher. This seems to be aimed only at the immediately family and mostly at you. He needs to see there are consequences to those behaviors and they won't be tolerated. Call his pediatrician and make an appointment for you to talk to him/her about your son's behavior. Cut out all violence he may be exposed to, TV, video games (and I am so not saying violent video games create violent children) etc. and set boundaries and follow through. I would also remove all sharp objects from his reach and hide anything that could be used as a weapon.