The heckling - which also included the words "make a change" - began as OH governor Mike DeWine spoke at the gathering, attended by hundreds. Assistant police chief Matt Carper named the gunman as Connor Betts, a 24-year-old white male from OH, and said his sister Megan Betts, 22, was among those killed.
Connor Betts, 24, was armed with a.223-calibre rifle with magazines capable of holding at least 100 rounds of ammunition when he fired off dozens of shots in a popular entertainment district, Police Chief Richard Biehl said.
"She had told me she liked my outfit and thought I was cute, and I told her I liked her outfit and I thought she was cute", Papillon said. Some reports said as many as 24 may have been injured in Dayton.
Whaley noted at a news conference that the city was still recovering from tornadoes that swept through western OH in late May, destroying or damaging hundreds of homes and businesses.
She said that the OR district was "one of the safest places in the whole region".
Sen. Sherrod Brown, D-Ohio, responded to news of the attack by tweeting that "thoughts and prayers are not enough" and calling for stricter gun control laws.
Police have said there was nothing in his background to prevent him from buying the firearm he used.
A shotgun was also found in his vehicle which was not used. "This is a nightmare for them and I think they are struggling as I think you can understand", he said at the news conference.
"I never heard him talk about violence, say a racist word, or anything like that", Kern said.
But high school classmates said he was suspended for compiling a "hit list" of those he wanted to kill and a "rape list" of girls he wanted to sexually assault.
The gunman, who has not been identified by authorities, was shot to death by responding officers.
The companion was wounded in the shooting, police said.
President Donald Trump was briefed on the shooting and praised law enforcement's speedy response in a tweet Sunday.
In all, there have been at least 32 mass shootings, defined as three or more killings in a single episode, in the United States this year.
The shooting happened in the area of East 5th Street in the Oregon District of Dayton in the early hours of Sunday local time and just hours after another mass shooting in El Paso, Texas.
The Ohio shooting was the third major outbreak of us gun violence, coming seven days after a teenager killed three people with an assault rifle at a food festival in Northern California before taking his own life.