I thought this was interesting from Wikipedia.
Sanford Police Investigation
Police officer Timothy Smith arrived at the scene at approximately 7:17 PM. He reported finding Zimmerman standing near Martin, who was lying face down in the grass and unresponsive.[15][18] At that time, Zimmerman stated to Smith that he had shot Martin and was still armed. Smith handcuffed Zimmerman and removed his weapon from him. Smith observed that Zimmerman's back was wet and covered with grass and he was bleeding from the nose and the back of his head.[15][105]
Ricardo Ayala, the second officer to arrive that night, noticed Officer Smith had Zimmerman in custody, then observed Martin lying face down in the grass and attempted to get a response from him. At this time, Sgt. Anthony Raimondo arrived and together with Ayala began CPR. Paramedics from Sanford Fire and Rescue arrived and continued CPR, finally declaring Martin dead at 7:30 PM.[15]
Other officers who had arrived by this time secured the area and made contact with neighbors in the area and obtained statements from witnesses at the scene. They did not realize Zimmerman had been in a vehicle, however, so it was moved before they could seize it.[106] Zimmerman was treated and released by paramedics while still at the scene of the incident.[15][105] After placing Zimmerman in his police vehicle, Officer Smith heard Zimmerman say, "I was yelling for someone to help me, but no one would help me."[15][107] Zimmerman was then transported to the Sanford Police Department where he was questioned by investigators for approximately five hours.[15][19] The police determined that Zimmerman yelled for help at least 14 times in a 38 second span.[108] The question of who was calling for help has been disputed since then by others and remains inconclusive.
Guess who said they were yelling for help when being put in the police car at the scene? Zimmerman. Guess who had wet grass stains on their back?Zimmerman. Guess who was laying face down on the grass? Martin. That indicated Martin was on top like he said. The reports said the gun was 2-4 inches from the victim when he was shot.