DAYTON, Ohio — The FBI says Dayton mass shooter Connor Betts fantasized about mass shootings and murder-suicide for at least a decade before his 2019 attack that left nine dead.
The FBI says Betts didn't share specific details with friends or family about his fantasies.
The agency said Monday that a phenomenon known as bystander fatigue may account for why no one reported Betts to authorities.
The term refers to people becoming inattentive to concerning behavior by people they've known for a long time.
The FBI concluded its investigation Monday by saying Betts acted alone and a variety of mental health issues contributed.