According to the Orlando Sentinel, Trayvon did not die instantly and survived for several minutes.
As reported by the Sentinel:
"You're talking about minutes, at least, for him to survive," said Dr. William Anderson, a forensic specialist and former deputy medical examiner for Orange and Osceola counties. "I think he would have been conscious … for a little time anyway."
What killed the Miami Gardens teenager was blood loss, massive internal bleeding, said Anderson and Dr. William L. Manion, a board certified anatomical, clinical and forensic pathologist and lawyer in Mt. Holly, N.J.
Trayvon’s chest cavity had filled with 2,300 milliliters of blood, according to the autopsy. That's about one-third of a healthy person's total blood volume, Anderson said.
Trayvon's heart had kept pumping, both pathologists said, but with each contraction, blood was leaking or gushing into his chest, depending on the size of the bullet hole.
The two doctors agreed that Trayvon remained conscious for a time. Anderson suggested the teenager may have been conscious for several minutes. Manion estimated it at just 20 to 30 seconds.
Zimmerman is currently free on $1 million bond awaiting trial on a second-degree murder charge.
SOURCE: Orlando Sentinel