DAYTON, Ohio (AP) — The gunman who killed nine people in Dayton, Ohio, had expressed a desire to commit a mass shooting and showed an interest in violent ideology, investigators said Tuesday as the FBI announced it is opening an investigation.

Federal investigators will try to determine what ideologies influenced 24-year-old Connor Betts, who might have helped him or knew in advance of his plan, and why he chose the specific target of Dayton's Oregon entertainment district for the shooting early Sunday, said Special Agent Todd Wickerham, the head of the FBI's Cincinnati field office.

Dayton Po...