Yes, well, you can tell from the 911 call that he did not simply approach TM and ask "Excuse me young sir, but might I ask what your business is tonight?"
he did NOT say, I am with neighborhood watch why are you here?
The girlfriend was pretty clear when she demonstrated what she heard which was a pretty belligerant "WHAT ARE YOU DOING AROUND HERE?"
If he wanted to and thought he could resolve things peacefully then his method truly sucks....and yes following someone and asking what they are doing in a certain way is in fact an aggressive act, and gives every indication that you want to start a physical fight.
My personal opinion is that everything that I have heard leads me to believe that he had every intention of starting a physical fight, and he wasn't afraid because after all he had a gun.