The Republican candidate for Montana’s congressional seat has been charged with misdemeanor assault after he is alleged to have slammed a Guardian reporter to the floor on the eve of the state’s special election, breaking his glasses and shouting, “Get the hell out of here.”

Ben Jacobs, a Guardian political reporter, was asking Greg Gianforte, a tech millionaire endorsed by Donald Trump, about the Republican healthcare plan when the candidate allegedly “body-slammed” the reporter.

“He took me to the ground,” Jacobs said by phone from the back of an ambulance. “I think he wailed on me once or twice … He got on me and I think he hit me … This is the strangest thing that has ever happened to me in reporting on politics.”

Jacobs subsequently reported the incident to the police. The Gallatin county sheriff’s office said on Wednesday night it had completed its investigation and that Gianforte had been issued with a charge of misdemeanour assault.

“Following multiple interviews and an investigation by the Gallatin county sheriff’s office it was determined there was probable cause to issue a citation to Greg Gianforte for misdemeanor assault,” sheriff Brian Gootkin said in a statement. “The nature of the injuries did not meet the statutory elements of felony assault. Greg Gianforte received a citation on Wednesday night and is scheduled to appear in Gallatin county justice court between now and June 7, 2017.”

A statement by campaign spokesman Shane Scanlon blamed Jacobs for the altercation, saying that he “entered the office without permission, aggressively shoved a recorder in Greg’s face, and began asking badgering questions”.

“Jacobs was asked to leave,” the statement reads. “After asking Jacobs to lower the recorder, Jacobs declined. Greg then attempted to grab the phone that was pushed in his face. Jacobs grabbed Greg’s wrist, and spun away from Greg, pushing them both to the ground.

Last month, the Missoulian newspaper took Gianforte to task for his attitude toward the press. At an event hosted by the Advancing Conservatism Society, an audience member reportedly said: “Our biggest enemy is the news media. How can we rein in the news media?”

Gianforte responded by pointing at a reporter and saying, “We have someone right here. It seems like there is more of us than there is of him.” The Republican later told the Billings Gazette that his comments were a joke.