TULSA, Oklahoma - Tulsa County reserve deputy Bob Bates has been charged with manslaughter in the death of Eric Harris. Bates, 73, shot and killed Harris during an undercover gun deal April 2, 2015.

The family of Eric Harris will hold a news conference at 4 p.m. at their attorney's office.

Harris became suspicious during the undercover sting and ran from police, according to Tulsa County Major Shannon Clark. Deputies took him to the ground during a struggle, and that's when Bates shot the 44-year-old man.

Bates thought he had pulled a stun gun, rather than his firearm when he shot Harris, according to sheriff's office investigators.

“Mr. Bates is charged with Second-Degree Manslaughter involving culpable negligence," said District Attorney Stephen Kunzweiler.

"Oklahoma law defines culpable negligence as ‘the omission to do something which a reasonably careful person would do, or the lack of the usual ordinary care and caution in the performance of an act usually and ordinarily exercised by a person under similar circumstances and conditions,'” Kunzweiler said.

4/13/2015 Related Story: Family Of Man Killed By Reserve Deputy Calls Shooting 'Evil'

“The defendant is presumed to be innocent under the law but we will be prepared to present evidence at future court hearings," he said.

Harris' family had a chance to review the video and released a statement before charges were filed against Bates, saying in part:

"We have now had the opportunity to review the heavily edited version of video released by the Tulsa County Sheriff's Office. This video shows a portion of the events which led to the untimely death of our loved one, Eric Harris. We have also heart TCSO's version of the incident and the findings from its internal investigation. We are saddened, shocked, confused and disturbed."

The family has not released a statement since charges were filed.