TAMPA, Fla. – A second autopsy shows that a 14-year-old boy who was punched and kicked by guards at a juvenile boot camp did not die of natural causes as a medical examiner initially ruled, prosecutors confirmed yesterday.

Martin Lee Anderson was sent to the Bay County Sheriff’s Office boot camp on January 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.

A noted pathologist who observed Monday’s 12-hour autopsy on behalf of Anderson’s family said it was clear the teenager did not die from sickle cell trait, as the medical examiner for Bay County had determined, or from any other natural causes.

Pam Bondi, a spokeswoman for Hillsborough County State Attorney Mark Ober, confirmed that assertion by Dr. Michael Baden but would not elaborate, saying it will be months be fore the investigation is complete.

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

Mr. Ober was appointed by Governor 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 yesterday. 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.