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Navy orders probe of DC rampage as shooter's remains released

The FBI released surveillance video of Aaron Alexis holding his shotgun and walking around the hallways where he shot his victims in the Washington Navy Yard. NBC's Pete Williams report.

The Navy ordered an investigation into the deadly Washington Navy Yard shooting on Thursday, and the D.C. medical examiner released the gunman’s remains.

Navy Secretary Ray Mabus issued a memo ordering the in-depth probe, which will include a detailed review of the events leading up to the shooting in which Aaron Alexis, a former petty officer, was able to enter the Navy Yard with a shotgun and roam the halls looking for targets.

The investigation will also look into the shooter’s mental health background as well as his military record, The Associated Press reported.

The FBI is also conducting its own criminal probe of the case.

FBI via AP

Aaron Alexis in an undated photo released by the FBI.

Burning questions remain on circumstances surrounding the shooting, including whether Alexis’ employer, a Hewlett-Packard subcontractor, The Experts, had warned the military about concerns about Alexis’ mental stability.

Navy officials have said they could find no record the company alerted the Navy.

Alexis killed 12 people and wounded four others in a hours-long rampage through Naval Sea Systems Command on Sept. 16 before he was killed in a shootout with police on the third floor of Building 197.

Also on Thursday, a spokeswoman for the Chief Medical Examiner’s Office in Washington, D.C., confirmed to NBC News that an autopsy had been completed on Alexis' body and his remains had been released.

She declined, however, to say who claimed the body or provide the results of the autopsy.

On Wednesday, HP issued a statement that it was cutting ties with The Experts over its “failure to respond appropriately” to Alexis’ mental health issues. That move came shortly after the FBI disclosed that Alexis had been suffering from a “delusional” belief that he was being controlled by “low frequency electro-magnetic waves.”

Rhode Island police said last week it had reported concerns to the Navy last August after Alexis called them to complain he was hearing voices and believed he was under surveillance while he worked on another job for IT contractor in that state.

Mabus named Adm. John Richardson, head of the Navy’s Nuclear Propulsion Program, to lead the new investigation, which will look into whether Navy policies were followed regarding security clearances, building protection and emergency responses.

Both the AP and Reuters said they had obtained the memo issued by Mabus ordering the investigation, which called for the probe to be finished by Nov. 6.

Michael Isikoff of NBC News and The Associated Press and Reuters contributed to this report.