The FBI will join Dayton police in investigating this past weekend's mass shooting, with authorities focused on the killer's "violent ideologies," officials said Tuesday.

Federal and local authorities have thus far stopped short of calling the murder of nine people, in Dayton's downtown entertainment district early Sunday morning, a terrorist act by Connor Betts, 24.

Betts was killed by responding police.

"Our investigation with Dayton police is ongoing, we have not made any final investigative conclusions into the motive of the shooter or if he was assisted by any other people in this attack," Special Agent Todd Wickerham, head of the FBI's office in Cincinnati, said at a press conference.

"However, we have uncovered evidence throughout the course of our investigation that the shooter was exploring violent ideologies," Wickerham said.

"Based on this evidence, we’re initiating an FBI investigation, side-by-side with the Dayton police homicide investigation, to make sure we get to the bottom and we explore everything and we try to understand the best we can why this horrific attack happened."

And Dayton Police Chief Richard Biehl said his investigators have found that Betts had a "history of obsession” with violence and "had expressed a desire to commit a mass shooting."

The Dayton announcement comes on the same day the FBI said it will investigate the shooting at the Gilroy Garlic Festival as domestic terrorism, similarly citing the "violent ideologies" of deceased gunman Santino William Legan. Three people were killed during the July 28 attack in Northern California before Legan turned the gun on himself.

Federal authorities are also investigating Saturday's mass shooting at a Walmart in El Paso, Texas, as domestic terrorism. The suspect, Patrick Crucius, is in custody for allegedly killing 22 people in what officials say was an attack "designed to intimidate a civilian population."

Betts' ex-girlfriend Adelia Johnson, 24, told the "Today" show, in an interview which aired Tuesday, that the killer often brought up mass murders when they spent time together.

"He would have known that his actions were deplorable," Johnson said about the man she dated earlier this year.

It also still wasn't clear by Tuesday if Betts targeted his sister, who was among those killed in Dayton's popular Oregon District.

And even though six of the nine victims were African Americans, authorities also insisted there was no immediate evidence that Betts acted out of racial hatred.

"We have not found any indication that it was a racial motivation at this time," Wickerham said.

President Donald Trump is set to visit Dayton on Wednesday.

Mayor Nan Whaley, a Democrat, said she'd greet the president, but encouraged constituents to protest Trump when he's in southwest Ohio.

"He’s made this bed and he’s got to lie in it," Whaley told reporters Tuesday. "His rhetoric has been painful for many in our community and I think people should stand up and say they're not happy."

Whaley took a dig at Trump's verbal misstep when, on Monday, he offered condolences to the people of Toledo — which is 150 miles north of Dayton.

A reporter asked Whaley for her reaction to Trump "when he addressed the nation about the shootings, when he addressed the people of ..." And that's when the mayor jumped in to complete the sentence, blurting out, "of Toledo."

Whaley accused Trump of being a coastal elite who views Ohio through a narrow lens. "People from the coasts never understand Ohio and they think all Ohio cities are the same and it’s an exhausting issue that we have all the time," she said.