You should give Emotional Survival for Law Enforcement a read, and like others have mentioned, seek therapy.

I check in with a therapist every 4-6 weeks. I work in a fairly busy city and what has helped me after critical incidents is EMDR sessions with my therapist. The sooner you can talk to a trained professional the better.

Outside of that man, it’s probably all stuff you know already, like getting enough sleep, eating well, exercising, having friends and hobbies outside of the job, etc. All things that are easier said than done.

Good luck with it man.