I can't speak for everyone, but with me its manifested in hyper vigilance/fuck being in large crowd/ unable to stay asleep long than 3 hours at a time. Its possible that PTSD may cause sudden mood swings causing bursts of anger. There has been a case of Vietnam vet having flashback causing them to get violent at a Burger King. It's a complicated mental disorder that manifests itself in so many ways that we just don't have all the scientific answers yet.
That said: Would you purposely take someone to a gun range for "therapy" without making sure ahead of time that they (possibly) don't get triggered while holding a gun?
I don't disagree that it's a "complicated mental disorder." But that's the thing: It's extremely complicated and I'm not sure I'd trust taking someone to the range until you were pretty sure it wasn't going to cause them to have a flashback/trigger and lose control?