A gunman in body armor opened fire early Sunday in a popular entertainment district in Dayton, Ohio, killing nine people, including his sister, and wounding dozens of others before he was quickly slain by police, city officials said.

Connor Betts, 24, was killed by police less than a minute after he started shooting a .223-caliber rifle in the streets of Dayton’s historic Oregon District about 1 a.m. in the second U.S. mass shooting in less than 24 hours. Police haven’t released further information about Betts or publicly discussed a motive.

His 22-year-old sister Megan was the youngest of the dead — all killed in the same area of bars, restaurants and theaters that is considered a safe area downtown, police said.

Dayton Mayor Nan Whaley said the shooter was wearing body armor and had additional high-capacity magazines. Had police not responded so quickly, “hundreds of people in the Oregon District could be dead today,” she said.

Six of the nine killed were black, police said. Although they’ll investigate the possibility of a hate crime, they said the quick timing of the violence made any discrimination in the shooting seem unlikely. Police said Connor Betts, who was white, was killed in less than a minute by officers patrolling in the area.

They identified the other dead as Monica Brickhouse, 39; Nicholas Cumer, 25; Derrick Fudge, 57; Thomas McNichols, 25; Lois Oglesby, 27; Saeed Saleh, 38; Logan Turner, 30; and Beatrice N. Warren-Curtis, 36.

Whaley said at least 27 more people were treated for injuries, and at least 15 of those have been released. Several more were in serious or critical condition, hospital officials said at a news conference Sunday morning. Some suffered multiple gunshot wounds and others were injured as they fled, the officials said.

Staff of an Oregon District bar called Ned Peppers said in a Facebook post that they were left shaken and confused by the shooting. The bar said a bouncer was treated for shrapnel wounds. Their Facebook and website post read: