The gunman who opened fire on a Northern Illinois University classroom on Valentine's Day had traces of nicotine, cold medicine and an anti-anxiety drug in his system, authorities say.

Toxicology tests and an autopsy of former NIU student Steven Kazmierczak, who shot and killed five students before taking his own life the, showed he had less than .025 micrograms of the anti-anxiety drug Alprazolam, also known as Xanax, according to a report in the Chicago Sun-Times.

Despite trace amounts of drugs in Kazmierczak's system, experts say it's unlikely any of them would lead someone to violence.

"This combination of drugs in his system could have no effect whatsoever on his mental status," Angelos Halaris told the Sun-Times, chairman of the Department of Psychiatry and Behavioral Neurosciences at Loyola University Medical Center.

Kazmierczak died of a "contact-range gunshot" wound to his mouth, according to the autopsy report.

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