R. Paul makes sense in a vacuum!
In the real world many take solace in shooting and doing thing we have spent years in training to do! We do them because we enjoy those activities! It's therapy to me and to many friends of mine! So, have severe PTSD and I know them well! Know when and where I must intervene to keep the peace! PTSD or not! There is no reason to shot another man that has come to your aide!
The shooter had mental problems! Proof is in the results!
However, I submit there is more to this than has been reported! Why did the mentally ill man run?