Montgomery County coroner Kent Harshbarger says Connor Betts, 24, had a pipe device and a baggie of cocaine with him, and cocaine, alcohol and an antidepressant in his blood.

Harshbarger also reported in his preliminary autopsy findings that police stopped Betts with at least two dozen gunshots that hit him at gaps in his body armour.

Dayton Police Chief Richard Biehl said the intense firefight that occurred was a rare situation.

"The officers were confronted with a moving shooter wearing body armour, actively executing victims with an AR-15 type weapon and high capacity magazines," he said on Thursday.

The coroner said police gunfire hit two people. One of them died, but Harshbarger said the gunman, not police, fired the lethal round.

Meanwhile, Betts' parents have apologised for the wording in his obituary that didn't mention the mass shooting, whose victims included his younger sister.

Stephen and Moira Betts issued a statement that said the obituary for Connor Betts was "insensitive in not acknowledging the terrible tragedy that he created".

They said they wanted to reflect the son they knew and weren't trying to "minimise horror of his last act".

The obituary described Betts as a "funny, articulate and intelligent man with striking blue eyes and a kind smile" before it was taken down on Wednesday by a funeral home in their hometown of Bellbrook, Ohio.

Betts opened fire in a popular entertainment district in Dayton. Police shot him as he neared a crowded bar.

It's not known whether Betts targeted his 22-year-old sister, Megan. They had spent an hour together at a bar in the same area before the shooting.

Australian Associated Press