I had for most of young adult life depression and those thoughts. I got help from therapists over the years. One day, it dawned on me it was a yo-yo effect(depression <-> anxiety) . All had to do was wait it out and it would go away. It’s that simple for me, maybe it’s that for others. Then I learned deep meditation to balance my ADD (extreme) emotions. I would/do spend about 20 mins and I would be back to normal(for me) whenever needed.
As for violent thoughts, I see it as part of ADD. Our emotional regulator is defective. Some people use physical things like hitting a bag, etc, as an outlet. Some use video games. I’v read that many people in prison have ADD. As long as you keep it in the game and out of the real world, you’ll be fine
If I have a bad day, I play violent video games to get the anger out my system: Crysis, The Witcher, Oblivion, F.E.A.R., Empire Earth. I’m totally different in game. Depending on the game, i’ll wipe out everything and leave nothing standing or alive and enjoy it. Afterward, my mind is clear and i’m more able to rationally deal with the real world. Also, I’v been playing these type games for about 30 years. I’m about as non-violent as you can find. 
Just remember your wired differently. Most of us have Yo-Yo emotions. Know that whenever the thoughts come around. Also, I dealt with bullies myself, but i’m still here. Our emotions can overwhelm us, the spikes up and down. When your a teenager, it’s “i’m trapped and there is no way out.” However, as an adult with wisdom. You know it’s just temporary. When I was teenager, I learned specific deep meditation techniques to balance my emotional states.
Don’t blame yourself for not seeing it coming. My parents never knew about those thoughts in myself and they don’t to this day.
REPORT ABUSE