Trayvon Martin died from a single gunshot wound to the chest fired from “intermediate range,” according to an autopsy report on the Florida teenager reviewed Wednesday by NBC News.

The official report, prepared by the medical examiner in Volusia County, Fla., also found that Martin, 17, had one other fresh injury – a small abrasion, no more than a quarter-inch in size – on his left ring finger below the knuckle.

Separately, a medical report on Martin’s killer, 28-year-old George Zimmerman, prepared by his personal physician the day after Martin’s shooting in Sanford, Fla., on Feb. 26, found that the Neighborhood Watch volunteer suffered a likely broken nose, swelling, two black eyes and cuts to the scalp. That report, first reported Tuesday by ABC News, also was reviewed by NBC News.

Both documents are part of a mountain of evidence – up to 300 pages and 67 CDs of witness statements, surveillance videos and other material-- expected to be made public soon in connection with the second-degree murder case against Zimmerman.

At the heart of the case is what happened of the course of 90 seconds: from the moment Zimmerman hung up with a non-emergency dispatcher to the first 911 call from a neighbor reporting the shooting.

CBS News reported Wednesday that a responder at the crime scene said he and others saw wounds on the knuckles of one of Martin's hands as he lay dead on this lawn, suggesting Martin had thrown a punch.

Zimmerman told police he fired the shot at point blank range while on his back, as the 17-year-old straddled him.

He also told investigators Martin did not die immediately but mumbled either it's over or you got me.

Special prosecutor Angela Corey's team has built a murder case against Zimmerman on evidence not available to the original state attorney or Sanford police - information that includes the autopsy report on Martin.

State crime lab analysis of his clothes, including gun powder residue that could indicate the distance between of the men.

Cell phone records from Zimmerman that include text messages he sent up to one month after the shooting

There are also two surveillance videos, one from the 7-11 where Martin bought Skittles and an ice tea, the other from the clubhouse in the gated subdivision where Zimmerman shot him.

The special prosecutor's case also includes Zimmerman's medical report the day after the shooting. It listed a broken nose, two black eyes and a cut in the back of the head.

On April 11, Zimmerman was charged with second-degree murder. He was released on April 23 on a $150,000 bond and has been out of the public eye since then.