[The Dayton gunman had a history of threatening women, said former friends.]

Investigators are trying to learn more about the relationships among the suspect, identified by the police as Connor Betts; his sister, Megan Betts; and the mutual friend, who is being treated for a gunshot wound in his lower torso. His name has not been released.

The three drove to the Oregon entertainment district in Dayton together on Saturday night, and then separated, although they remained in touch. The police have said there was no indication that the sister or mutual friend knew that Mr. Betts was armed.

The gunman fatally shot one person in an alleyway before turning his fire on his sister and their friend, the police have said. At least 27 people were wounded, including 14 who were shot; the rest had cuts and injuries from the stampede of fleeing people.

Mr. Betts had purchased his AR-15-style rifle legally online from Texas, and had it shipped to a gun store in or near Dayton, the police said, adding that it had been modified with a pistol brace to improve stability.

He had a drum magazine that could hold 100 rounds, the police said, and enough magazines to hold up to 250 rounds of ammunition. He fired at least 41 shots, Chief Biehl said. Six officers fired a total of 65 rounds at the gunman, killing him as he tried to enter a bar, where many people had taken refuge when the shooting began.

The chief said that, based on the information currently available, “we are not seeing any indication of race being a motive.”