The toxicology tests, performed as part of Seung-Hui Cho's autopsy, answered one of the key remaining questions in the investigation of the gunman who opened fire April 16 in a dormitory and a classroom building.
Cho, 23, shot himself as officers closed in. His autopsy report confirmed that he died from a self-inflicted gunshot wound to the head, police said.
State police said they will not release the complete autopsy reports on Cho or his victims because the criminal investigation is ongoing.
A state panel investigating the shootings is reviewing Cho's contact with the mental health system. Cho was ordered into involuntary outpatient treatment in 2005 after a judge found that he was a threat to himself. But there is no indication he ever received treatment.