Dayton police showed a photo and provided detail on the gun the suspect used in the attack.
Police Chief Richard Biehl told the media the weapon has a "double drum magazine" which has a capacity of up to 100 rounds.
Biehl said the gun was purchased legally. He said the gun was ordered online from Texas, then transferred to the suspect at a local firearms dealer in Ohio.
Biehl added that police weren't aware of anything "in this individual's history or record that would have precluded him from purchasing that weapon."
Asked by reporters about the legality of the large magazine, Biehl said there is "no indication that that is illegal at this time."
Biehl said the suspect fired "dozens" of shots during the shooting.