The suspect who opened fire outside a crowded bar in downtown Dayton, Ohio, killed his own sister during the attack, which left nine people dead and 27 more injured, according to authorities.
Megan Betts, 22, was killed around 1:05 a.m. Sunday after her brother, 24-year-old Connor Betts, attacked revelers outside Ned Peppers Bar with a .223-caliber rifle, armed with multiple 100-round capacity magazines.
Dayton Police Chief Richard Biehl said Monday the shooter's motive remains unclear but added that authorities don't see how he could have killed his sister at random, according to ABC News.
"It seems to just defy believability that he would shoot his own sister, but it's also hard to believe that he didn't recognize that was his sister," Biehl said. "So we just don't know."
Megan and her brother, both of Bellbrook, had traveled to the Oregon District, a popular nightlife area, together in the same car with another male companion before separating at some point over the course of the evening, NBC News reports.
Connor later returned from an alleyway near where the vehicle was parked wearing a bulletproof vest and hearing protection and opened fire. His sister and the male companion, whose identity has not been released, were the second and third victims gunned down, police say. The male survived the attack and is reportedly cooperating with authorities.
Responding officers engaged and killed the shooter "instantaneously and effectively," ending the rampage "in 30 seconds" and preventing much more bloodshed, Chief Biehl told reporters after the attack.
"Had this individual made it through the doorway of Ned Peppers with that level of weaponry, there would have been catastrophic injuries and a loss of life," he added.
A friend of Megan's, 20-year-old Dana Raber, told reporters Sunday the victim was "wonderful" and "different in a very good way."
"That's why we got along, I supposed," Raber recalled. "She's very sweet, had her own opinions and was loud and kind in a way that her brother was quiet and stayed more to himself."
Raber also said she was unaware of any issues between Megan and her brother that could have prompted the fatal incident.
"They are a family I admired, and I don't know how they're going to get through this," she said. "They were always very nice to me."