Did Orlando Shooter Have 'Roid Rage'?

New information leaked by federal investigators raises the possibility that steroid use could have been a factor in Omar Mateen's attack on patrons of Orlando's Pulse nightclub.

An autopsy has indicated he was "likely a long-term user of steroids," the Los Angeles Times reports, citing two anonymous federal law enforcement officials.

"Federal investigators are not sure if steroids played a role in the shooting," the Times reports. "A medical examiner found evidence of physical changes to Mateen's body that were consistent with long-term steroid use, the officials said, and is seeking to confirm that assessment through further testing."

Mateen, using a military-style semi-automatic rifle, opened fire in the gay club in the early hours of June 12, killing 49 people and wounding 53. He died in a shootout with police.

In trying to determine Mateen's motivation, police and the media have looked at several factors. He is said to have embraced a radical form of Islam and to have pledged allegiance to the terrorist group known as the Islamic State of Iraq and Syria. He is said to have been offended by the sight of two men kissing. Others, however, have said he had profiles on gay dating apps. His ex-wife raised the possibility that he was gay, and she and a former coworker said he was a steroid user.

Anabolic steroids, used by some people to build muscle mass, mimic the action of testosterone. This often leads to an increase in aggressive behavior by users, especially men. Some extreme forms of aggression, including homicidal behavior, have been blamed on excessive steroid use, in a phenomenon popularly dubbed "roid rage." Doctors don't universally believe in this phenomenon, but those who do say it is indeed implicated in murders.

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"Research shows conflicting results for the existence of steroid-induced rages," Live Science reported in 2013. "If they do exist, they happen rarely, and likely only among excessive users with pre-existing psychological issues."

Physician Gary Wadler, though, told Web MD in 2007 that roid rage exists and has been a factor in several homicides. There "is a spectrum of behaviors by people on anabolic steroids ranging from being somewhat more assertive, moving up one notch to being frankly aggressive, and moving up another notch to actually having this roid rage," he said. "It's really an extreme of a spectrum of kind of behavioral things that you see with anabolic steroids."

The National Institute on Drug Abuse takes a cautious view on its website, as quoted by the Times, saying steroids "increase irritability and aggression. Some steroid abusers report that they have committed aggressive acts, such as physical fighting or armed robbery, theft, vandalism, or burglary."

In several high-profile murder cases, lawyers and investigators have raised the possibility of roid rage as a contributing factor, but the evidence remains inconclusive. During the trial of former Olympic runner Oscar Pistorius for the fatal shooting of his girlfriend, Reeva Steenkamp, there was speculation about roid rage, but it apparently did not figure in a judge's recent sentencing of Pistorius to six years in prison. Pistorius has long claimed that mistaken identity was to blame for the 2013 shooting, saying he mistook Steenkamp for an intruder.

Meanwhile, in another set of anonymous comments attributed to a U.S law enforcement official, The Washington Postreports the FBI found no evidence that Mateen was antigay. The official told the newspaper that, "While there can be no denying the significant impact on the gay community, the investigation hasn't revealed that he targeted Pulse because it was a gay club."