At least nine people were killed and 27 injured in a mass shooting in Dayton, Ohio, early Sunday morning, officials said the second horrific slaughter in America in less than 24 hours.

The assailant has been identified as 24-year-old Connor Betts. His brother, Jordan Cofer, was among the shootings fatalities, police said at a Sunday press conference.

Connor Betts was armed with a legally obtained .223-caliber rifle with 100 round drum magazines when he carried out the assault in the citys downtown Oregon District around 1 a.m, said Dayton Police Chief Richard S. Biehl. Betts was wearing a mask, bulletproof vest and hearing protection.

Any suggestion of motive is irresponsible, Biehl said, adding that the motivation may not even be understandable.