US Attorney Benjamin Glassman stressed that Kollie is not accused of intentionally taking part in the planning of the shooting.
The killings, which came just hours after a shooter in El Paso, Texas shot dead 22 people has raised questions over the process of purchasing guns in America.
Police have said there was nothing in Betts’ background that would have prevented him from buying the AR-15 style gun used in the shooting.
The weapon was bought online from a dealer in Texas and shipped to another firearms dealer in the Dayton area, police said on the day of the shooting.
Eight of Betts’ victims were shot multiple times, according to the Montgomery County coroner’s office. More than 30 others were left injured, including at least 14 with gunshot wounds, hospital officials and investigators said.
Just days after the shooting, the state’s Republican Governor, Mike DeWine, announced a package of gun control measures, including requiring background checks for nearly all gun sales in Ohio and allowing courts to restrict firearms access for people perceived as threats.