Feb. 10 (UPI) -- Stephen Paddock, who shot and killed 58 people in Las Vegas last fall, had anti-anxiety medication in his system, according to an autopsy report.
But the autopsy report released Friday provided no insight into what contributed to his motives.
"It seems that based on the autopsy reports there were no physical excuses for what Steve did," his younger brother Eric Paddock, who lives in Orlando, Fla., told the Las Vegas Review Journal. "We may never understand why Steve did this."
Paddock, 64, died of a self-inflicted gunshot wound to his head after he opened fire at an outdoor concert on the Las Vegas Strip from his 32nd-floor Mandalay Bay suite.
Dr. Lisa Gavin of the Clark County coroner's office performed the autopsy on Oct. 6, five days after killings. Judge Timothy Williams ordered Clark County Coroner John Fudenberg to turn over Paddock's autopsy records to news organizations.
Nordiazepam, oxazepan and temazepan, indicating the possible presence of the anti-anxiety drug Valium, were found in his urine, a toxicology report shows. No alcoholic substances were listed in the report.
Small amounts of arsenic and lead were found in his system. Neither of these substances would contribute to "violent and aggressive behavior," forensic toxicologist Laura M. Labay said. She works for NMS Labs, a private clinical and forensic toxicology lab in Pennsylvania that reviewed the results at the coroner's office request.
Labay noted that mercury levels can rise with seafood consumption or environmental exposure.
A separate examination of his brain at Stanford University found no major abnormalities, including no evidence of Alzheimer's disease.
The brain had "the most striking abnormality" in the hippocampus, a part of the brain involving human learning and memory. The report did not say if these abnormalities might have affected his behavior.
Paddock also was listed in the report as having hypertensive cardiovascular disease.