Advice needed

Kyla • I`m 26, a native of Colorado Springs, CO. I have a degree in surgical technology. As of right now I`m taking life one day at a time dealing with serious medical problems but staying positive.
A very close friend of mine died last year from a gun shot wound. He was a veteran and the police automatically ruled it a suicide even though 2 people were in the house with him, none of the standard tests were done. We've talked to the DA and he refuses to look further into it even after a private investigator found problems in the police report. We have started a petition to have them reopen his case but so far we have had no luck. We just want to know what truly happened that night, why police statements do not add up, and why no test were done to confirm that it was truly a suicide. We feel like once they knew he was a veteran in counseling for PTSD they didn't bother to look for the truth, it's almost like it was an easy way out. If anyone can give me any advice I would greatly appreciate it! He left behind 3 daughter, his mother and father and a lot of loved ones.