Maybe he was out there that late to sell drugs or rob an all night gas station. Maybe, he was conspiring to get another gang tattoo or more gold teeth.
These are only things that Trayvon would have known and Zimmerman as a trained officer of the neighborhood watch would have observed.
True, he could have been stalking the streets at 3 in the morning, even on 2/26. But by 7:30 pm that evening he was deceased.