The ex-girlfriend of the man who shot nine people dead in Ohio has said there were "red flags" that suggested he might be capable of an attack.

Adelia Johnson added that Connor Betts, whose sister was among those he killed in Dayton on Sunday, had long-wrestled with mental illness that manifested itself in a fascination with tragedy.

She also said the 24-year-old once "got super drunk and told me he wanted to hurt people".

Ms Johnson, who dated Betts for a few months earlier this year, added that he had suicidal thoughts so deep he twice put a gun in his mouth, ready to pull the trigger.

Speaking about the mass shooting in Ohio, she said on Tuesday: "I have no idea what his motivation was.


"I will never know."

Ms Johnson, 24, wrote a 2,200-word document recounting her relationship with Betts, which she sent to reporters and posted online.

In it she wrote: "There wasn't a hate crime.

Image: Adelia Johnson has said Betts told her he 'wanted to hurt a lot of people'

"He fought for equality. This wasn't a crime of passion. He didn't get passionate enough. This wasn't very premeditated.

"He wasn't a thorough planner."

Ms Johnson said the tone was set on their first date when Betts showed her a video of last year's Pittsburgh synagogue shooting and narrated it play-by-play.

He later steered towards conversations about world tragedies and suicidal thoughts.

Ms Johnson writes in her letter: "He trusted me with so much of his darkness that I forgot most of it."

She added that she brushed off much of what she heard.

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Ms Johnson said he would talk about serial killers, but it made sense because it was a theme in a psychology class they were taking at Sinclair Community College in Ohio.

She added that a captivation with disaster and violence was offset by the sweetness of a "perfect gentleman," and joking about a desire to hurt others was seen as the coping tool of a man grappling with illness.

Image: Betts killed his sister Megan in the attack

Ms Johnson said in her interview on Tuesday: "He was super nice to me. Super nice to everyone that I saw him interact with. He was never mean to anyone. (But) apparently he had that in him so."

She continued: "I didn't think that he would ever go to like some random place and just shoot random people.

"Obviously his sister wasn't random or maybe she was she just got crossed in the cross hairs. I don't know. But I wasn't entirely surprised that he did something bad. That he ended up in the news. I just didn't think it would be for this."

Ms Johnson said she and Betts bonded over their problems with mental illness.

He told her that he had bipolar disorder and might also suffer from obsessive-compulsive disorder.

Ms Johnson also said he confided in her that while he loved guns, he didn't believe those with mental illnesses should be allowed to have them.

Betts' high school classmates said he was once suspended for compiling lists of students he wanted to rape or kill.

Ms Johnson said that during her relationship with him there were two moments that stood out to her as "red flags".

She said that while he was travelling to Illinois for a gig with his heavy metal band, a drunk and slurring Betts called her and said something about how "he wanted to hurt a lot of people".

Ms Johnson also said that Betts was planning to leave a letter at the home of an ex-girlfriend in May that warned her: "You can't outrun your past."

She said Betts had tried to downplay it as a joke but she knew it wasn't.

When she pushed him to explain she said he spoke of "uncontrollable urges to do things", including a time he set fire to an abandoned building.

Ms Johnson said the "red flags" are what made her call the relationship off in May.

When she broke up with him, she said she reached out to his mother to express her concern, but she didn't elaborate on what they discussed.

Ms Johnson said in her interview that when she received a text from a friend who knew Betts asking if he could be the gunman she didn't think it was possible.

Crowd runs for cover as gunman approaches

Though he had problems with his parents, she knew him to like his sister, who was among those killed.

Betts was gunned down by armed police within 30 seconds of launching the attack in the popular nightlife area in Dayton.

Ms Johnson wrote in her letter: "Him getting shot is exactly what he wanted.

"He would be the first one to tell you that he hated himself."

The Betts family released a statement through police on Tuesday night, saying they are devastated and are co-operating with the police's investigation.

The statement reads: "The Betts family would like to express their enormous gratitude and love for everyone that has reached out and given their support during this awful time.

"They ask that everyone respect the family's privacy in order to mourn the loss of their son and daughter and to process the horror of Sunday's events."