The gunman who killed nine people outside a US bar had cocaine, Xanax and alcohol in his system at the time, a coroner has revealed.
Betts carried out the most recent US gun massacre earlier this month, opening fire outside a bar in Dayton, Ohio.
Dayton police have today also admitted two victims of the massacre were struck by gunfire from law enforcement officers responding to the scene.
"While it weighs heavily on us that our response caused harm to these victims, we are comforted that none of our rounds caused the death of any of these innocent people," Dayton Police Chief Richard Biehl said on Twitter .
Dr Kent Harshbarger, Montgomery County coroner, said at a news conference an autopsy conducted on the body of 24-year-old Betts found the drugs and medication in his system.
It was not clear how much of each drug was present at the time of the attack.
The August 4 murders, which ended when police shot and killed the gunman, was one of three mass shootings over three weeks.
Earlier this week a friend of Betts, 24-year-old Ethan Kollie, was charged in federal court with lying about his drug use on a form he filled out to buy a gun.
He has also been charged with possession of a firearm by an unlawful user of a controlled substance.
Prosecutors said Kollie admitted he had purchased body armor, an accessory for an AR-15 semi-automatic rifle and a 100-round double drum magazine that Betts used during the shooting.
Kollie kept the items at his apartment in the Dayton suburb of Kettering to conceal them from Betts' parents, according to court papers.
However Kollie is not accused of helping plan or carry out the attack.
Betts opened fire outside a bar in the Oregon District of Dayton at 1am.
The shooting ended rapidly when police moved in and shot Betts dead.
Those killed included Betts' 22-year-old sister, Megan.
The FBI said last week that Betts had a history of violent obsessions and had mused about committing mass murder before his rampage in Dayton's historic downtown.
