How can I get intervention for former military member without involving local law enforcement?

Contact the VA Medical in the area, tell them what you have observed, ask them to contact the person for their own safety.

You could do a personal intervention. Honestly more information would be useful. Are there kids involved? Drugs/alcohol? Is the soldier married? Is there any threat to the former military mrmber, is there any threat to the family involved. After I got out I became a doctor and I work with a lot of veterans. My first concern is the safety of the service member and their family, cops or no cops. I also understand the consequences of situations being blown out of proportion. You don't want him to end up with a criminal record. You don't want him ending up on a VA list of peope who lose their 2nd Amendment rights (which is VERY common). You don't necessarily even want VA treatment which consists mainly of drugs and SSRI's which oftentimes just make everything look nicer on the outside while the soldier continues to boil on the inside leading to inevitable worse problems down the road. We really need more info here.

Get ahold off your local Vet court and have them provide him a mentor

I am a law enforcement officer. Call local law enforcement and explain what's going on. Law enforcement will Baker act your friend. We are allowed to hold him up to three days unless a Dr finds he is OK and release him early. Either way he gets seen by a mental health professional. A Dr can also Baker act your friend. So you could go straight to a medical professional. You could also take him to a VA hospital to be seen. If you believe that he could hurt himself call law enforcement and explain what's going on. They will get him the help he needs. You could also talk with him and tell him you will go with him to get the help he needs.

Grrr Leave me alone! I'll come out when the game is over???