A second autopsy indicates that a 14-year-old boy who was punched and kicked by guards at a juvenile boot camp may not have died of natural causes as a medical examiner initially ruled, prosecutors said Tuesday.

Martin Lee Anderson was sent to the Bay County Sheriff's Office boot camp on Jan. 5 for a probation violation. A surveillance video showed guards kicking and punching him after he collapsed while exercising on his first day at the camp, and he died at a hospital early the next day.

The second autopsy was ordered after his parents questioned the findings of Bay County's medical examiner, who concluded the teenager died from complications of sickle cell trait, a usually benign blood disorder.

The new autopsy was conducted Monday by Hillsborough County Medical Examiner Vernard Adams and observed on behalf of Anderson's family by Dr. Michael Baden, a noted pathologist. Baden said it was clear the teen did not die from sickle cell trait, or from any other natural causes.

"My opinion is that he died because of what you see in the videotape," said Baden, referring to the surveillance video.

Baden, who reviewed medical evidence in the slaying of Martin Luther King Jr. and worked for a congressional committee that reinvestigated the assassination of President Kennedy, said it will be several weeks before Adams can determine the exact cause of death because tissue samples must be analyzed and other evidence considered.

Pam Bondi, a spokeswoman for Hillsborough County State Attorney Mark Ober, confirmed Baden's assertion but would not elaborate, saying it will be months before the investigation is complete. Ober was appointed by Gov. Jeb Bush to investigate the case.

Anderson's mother, Gina Jones, said she was glad the truth was out.

"But I already knew what the truth was. Now that the truth is out, and I want justice," she said.

The medical examiner who made the initial finding of sickle cell, Dr. Charles Siebert, won't comment until the investigation is complete, his office said Tuesday. A spokeswoman for the Bay County Sheriff's Office, which operated the camp, also declined to comment.

No guards have been arrested or fired but the camp has been closed.

The U.S. Attorney's office in Tallahassee and the Justice Department's Civil Rights Division also have opened investigations.