AUTHORITIES said the 24-year-old who killed nine people in a rampage in Dayton had a troubled past, including threatening fellow pupils in high school.

The gunman, wielding an assault-style rifle and wearing body armour and a mask, inflicted carnage on a neighbourhood known for its night life.

Police identified the shooter as Connor Betts (24) of Bellbrook, Ohio.

The slaughter began at about 1am on Sunday in the city’s Oregon District and ended very rapidly after police who were nearby moved in and shot him dead.

Those killed included Betts’ sister, and at least 27 people were wounded.

“We are very, very early in this investigation,” police chief Richard Biehl said on Sunday.

“Any suggestion at this time of a motive would be irresponsible. We don’t have sufficient information to answer the question everyone wants to know: ‘Why?’”

Authorities said Betts had been troubled in high school, at one point drawing up a “hit list” of students he wanted to kill or otherwise harm. Apart from his high school troubles, Betts had traffic tickets for speeding and other minor traffic offences.

He had been studying psychology at a community college and working at a restaurant.

In an online profile, Betts reportedly described himself as “Good under pressure. Fast learner. Eager to overachieve”.

Police said the rifle was fitted with an extended drum magazine that could hold 100 rounds. The gun was apparently bought legally online from a dealer in Texas and shipped to a local firearms dealer.

Betts’ sister Megan (22) was one of the first to be killed. Biehl said the siblings had arrived in the same vehicle with a third person earlier in the evening, but separated before the rampage.

Cops said the companion was wounded. The shooting took place just 13 hours after a mass shooting at a Walmart store in El Paso, Texas, where 20 people were killed and 26 others wounded.

The 21-year-old suspect in that shooting was arrested. – REUTERS