The FBI has opened an investigation into the Ohio mass shooting, citing the gunman's interest in violent ideology.

The head of the FBI's Cincinnati field office says investigators will try to determine what ideologies influenced 24-year-old Connor Betts. Special Agent Todd Wickerham did not specifically say what the FBI was investigating, but said the agency is looking into who might have helped Betts, and why he chose the specific target of Dayton's Oregon entertainment district.

Dayton's police chief says Betts had expressed "a desire to commit a mass shooting."

Betts was wearing a mask and body armor when he opened fire with an AR-15 style gun outside a strip of nightclubs in Dayton early Sunday. He killed his younger sister and eight others before officers fatally shot him less than 30 seconds into his rampage. (AP) 

Earlier, Republican Ohio Gov. Mike DeWine urged the GOP-led state Legislature to pass laws requiring background checks for nearly all gun sales and allowing courts to restrict firearms access for people perceived as threats.

Persuading the Legislature to pass such proposals could be an uphill battle. It has given little consideration this session to those and other gun-safety measures already introduced by Democrats.

DeWine’s Republican predecessor, John Kasich, also unsuccessfully pushed for a so-called red flag law on restricting firearms for people considered threats.

DeWine on Tuesday says Ohio needs to do more while balancing people’s rights to own firearms and have due process.

The governor was thrust into the gun debate this week after being met with chants of "Do something!" while he spoke at a vigil in Dayton for the victims who died early Sunday in the shooting outside a strip of nightclubs.

Police have said 24-year-old Connor Betts was wearing a mask and body armor when he opened fire with an AR-15 style gun.

Authorities have said there was nothing in the gunman's background that would have prevented him buying a weapon.

  

The family of the Ohio shooter and his sister who was among the nine killed has released a statement saying they are devastated, and cooperating with law enforcement's investigation.

  

The family offered "their most heartfelt prayers and condolences" to the victims killed.

  

The family thanked first responders for their swift action to minimize casualties, and requested privacy "in order to mourn the loss of their son and daughter and to process the horror of Sunday's events."

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