Id say get him evaluated as soon as possible. 8 is so young and can t imagine what his reality is.
The doctor should be aware of his behaviors and language. Another thing I think of is this...
A brain learns pathways. And the more a pathway is used appropriate or not, the brain is learning it over and over. It can become like second nature. For me, when the kids irritate me, should I yell and hollar? It's so easy to do so, but to mentally be aware and to hold back on things I may feel like doing.. . . .like yell and hollar, When I hold back and make myself act appropriately, my brain learns that also. The more i practice, the better I get. It's an example that might help you see why a behavior can get used too much or even get worse. I say get that bad behavior changed before a child gets too old where it's more challenging. It's hard to teach an old dog new tricks...... Good luck

Thank you. I or we as a family are trying. Joe's been diagnosed with PTSD, ODD, ADHD and Bipolar since the age of 5. He has taken from his bio mom and dad when he was 4. He has seen abuse and too many other things I don't want to mention. I read on PTSD AND ODD and thought that with a Loving family and good guidance that he could be a normal kid and just be a kid. Not Joe. He is always on edge. As he gets older I feel his outbursts get more violent. He is currently In a mental guidance unit for a week. He had an episode and I had to call the police. He threatened to chop my head off while I am sleeping... Therefore, the police had to take him. I am so sad for him. Yet he has no remorse when he says these things. It's obvious, his mom and dad's DNA were messed up or just seeing the violence in his life for the first 4years of his little life messed him up. I just want to have hope.

I hope things are going alright for you and your family. I turn to Philippians 4:6-8 usually.

6 Do not be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God.

7 And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus. 

8 Finally, brothers and sisters, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things. 

I find peace when I read the Bible, it reminds me of how much God loves me and cares about my troubles.

On another note, I believe the troubles Joe went through effected him to this extent. I'm fortunate that Ty isn't threatening to kill me. We are finally starting counseling though, I hope to find resolution to the issues he has with getting along with others, lying and not being able to take blame, his arguing and more over problem with some authority figures.
Sometimes I think Tys mom's behavior and influence have effected him.

I will pray for you, your family and Joe.