DAYTON, Ohio (AP) The gunman who attacked the nightclub district in Dayton, Ohio, this weekend fired so quickly that authorities say he probably wasn’t targeting anyone.

Beyond that, investigators deemed it too soon to say what touched off Connor Betts’ 30-second rampage that left nine people dead early Sunday.

Among the questions: Why would the 24-year-old have shot his 22-year-old sister Megan, the youngest victim? And what could authorities have done to prevent the attack that ended when officers gunned him down?

Some students who went to high school with Betts in a Dayton suburb note that he got suspended for making threats. School officials haven’t discussed those details.

Others considered Betts a nice guy. One friend even described him as “the kind of kid you’d want as a son.”

Associated Press writers Julie Carr Smyth in Dayton, Michael Balsamo in Orlando, Florida, and Kantele Franko in Columbus contributed to this report.