He was asked repeatedly to give his address and his phone number but refused.
He was running, or else he was far less fit than your average heavy set man.
Only a completely gung ho idiot who had left the realms of reality far behind would follow a man he assumed to be a criminal bent on criminal activity, with a gun. He absolutely should have assumed that Trayvon might be carrying a gun if he was in fact the criminal or gangbanger Zimmerman thought he was, and hence the operator's warning not to follow him, and the pleas for location information. Zimmerman said he would say where he was when he had Trayvon in his sights.
If it was a police non emergency number that Zimmerman called then he was in fact talking with a police officer.
From the Huffington Post:
'There is about a one-minute gap between when Zimmerman made the 911 call and when he came face-to-face with Martin that police say they're not sure what happened.
According to what Zimmerman told local officers, he lost sight of the teen and was returning to his SUV when Martin approached him and they exchanged words. He said Martin asked if he had a problem, Zimmerman replied no and reached for his cell phone. He then alleges that Martin said "well you do now" and punched him in the nose.
Zimmerman said he then fell to the ground and Martin got on top of him and began slamming his head into the sidewalk. Zimmerman said he began yelling for help.
An individual can be heard screaming on the 911 audio, however, there's been a dispute amongst witnesses as to whether it was Zimmerman or Martin who was crying for help.
According to authorities, Zimmerman then shot Martin at close range. When the local police arrived at the scene, they found Zimmerman with a bloody nose, swollen lip and lacerations in the back of his head. Although paramedics gave him first aid, he said he did not need to go to the hospital and sought medical treatment the next day.'
So not any sort of life threatening injury, and Zimmerman could have concluded after Trayvon didn't produce a gun but instead used his fist that he didn't actually have one. OTOH, reaching for his phone might have made Trayvon think that Zimmerman was reaching for a weapon. To stand back or run in that case would have been insane for Trayvon. Obviously confronting Zimmerman near the SUV was not smart, but it is not a crime to ask someone why they are following you.