Michigan authorities have filed criminal charges against a man accused of shooting an elderly woman campaigning against abortion rights in the shoulder while she argued with his wife last week.

Richard Alan Harvey, 74, had publicly claimed it was an accident when he shot the 84-year-old woman. But prosecutors from Ionia county, Michigan, charged him on Friday with one count each of assault with felonious assault, careless discharge of a gun causing injury, and reckless use of a firearm in a case that appears to serve as an extreme example of how heated the debate surrounding abortion in the US can become.

According to investigators, the woman who was shot was volunteering with an organization named Right to Life and going door-to-door asking voters to oppose Michigan’s protecting abortion rights during a ballot measure in November when she went to Harvey’s home near Lake Odessa on 20 September.

Harvey later told the local television news station WOOD that the woman, Joan Jacobson, was arguing with his wife, who supports abortion rights. The couple told Jacobson she was trespassing and she should leave, but Jacobson refused, according to what Harvey told WOOD.

Harvey eventually emerged from a barn at his home with a .22-caliber rifle belonging to his wife, aimed at a pine tree out front and fired a warning shot. Then, “without thinking”, he said, he tried to use the rifle to “club” away a clipboard that the volunteer was holding, fearing she would hit Harvey’s wife with it.

According to Harvey, one of his fingers accidentally pulled the rifle’s trigger, and the ensuing shot hit the volunteer in the right shoulder.

“It went off,” Harvey said of the rifle he had pulled. “It was an accident.”

Jacobson received medical treatment for her wound after driving herself to a nearby police department. She told WOOD that she was peaceful throughout the confrontation with Harvey and his wife, Sharon. Jacobson said she was walking away when she was alarmed to see Harvey coming up to her while holding a rifle.

“The thing that I noticed the most was that he had a gun, and it was a big gun,” Jacobson said to WOOD. “It was [a] long barrel and by the time that registered in my brain, I heard a shot and I felt some pain.”

Authorities did not immediately charge Harvey with a crime. But that changed after an investigation from Michigan state police and the Ionia county prosecutor’s office.

The most serious of the charges against Harvey was felonious assault, which can carry up to four years in prison upon conviction.

A judge arraigned Harvey on Friday. His bail was set at $10,000.

The US supreme court’s 1973 decision titled Roe v Wade established federal abortion rights. But, in June, the supreme court’s current conservative majority voted to repeal those rights and let states individually decide whether abortion should be legal in their jurisdictions.

The legislatures of many states have since implemented restrictive abortion bans without putting the issue to voters. Michigan, for its part, is letting voters decide on 8 November whether abortion rights should be protected in their state constitution.

Michigan’s abortion referendum is coming after 730,000 of the state’s residents signed a petition requesting a vote.