(Reuters) - A friend of the Ohio man who killed nine people, including his own sister, in Dayton this month will be charged on Monday with lying on a form related to guns, federal prosecutors said on Monday.
The Aug. 4 attack, which ended when police shot and killed the gunman, was one of a series of three-high profile mass shootings that stunned the United States and stoked its long-running debate on gun rights.
The office of U.S. Attorney Benjamin Glassman said charges against the friend, who was not identified, would be unsealed at 2 p.m. (1800 GMT) in Dayton.
The FBI said last week that the slain suspect, 24-year-old Connor Betts, had a history of violent obsessions and had mused about committing mass murder before his rampage in Dayton's historic downtown.
Betts, who is from the nearby suburb of Bellbrook, Ohio, was wearing body armour and a mask during the attack, opening fire with an assault-style rifle fitted with a high-capacity ammunition drum that could hold 100 rounds, police said.
His sister, Megan Betts, 22, was one of the first victims to be killed.
(Reporting by Peter Szekely in New York; editing by Jonathan Oatis)