A Michigan man used an an all-terrain vehicle to run over and critically injure an 80-year-old man who was putting a Trump sign in his yard, in what police have described as a politically motivated attack.

The 22-year-old suspect in Sunday’s vehicle-ramming in the city of Hancock called police to confess before apparently taking his own life, authorities say.

Before targeting the elderly man, police say, the suspect vandalised two parked vehicles, smashing the windows of one that displayed a Trump sticker, and damaging the tyres of another that had a sticker supporting police.

The rampage took place just over a week after a 20-year-old would-be assassin attempted to kill Donald Trump at a political rally in Pennsylvania.

"The crimes reported in the city of Hancock appeared to be politically motivated, involving victims who displayed Trump election signs as well as law enforcement appreciated stickers and flags commonly referred to as 'thin blue line' paraphernalia," the Houghton County Sheriff's Office said in a statement.

The 80-year-old man was taken to hospital with critical injuries after being struck from behind by the suspect's ATV.

On Monday, police went to a nearby home after receiving a call from a person who said he wanted to "confess a crime involving an ATV driver within the last 24 hours" and asking police to come pick him up.

When officers arrived at the home, they found the suspect dead from what they believe was a self-inflicted gunshot wound.

"What this has done to this community is pretty upsetting," Hancock Police Chief Tami Sleeman told the Detroit News. "Our concern is the safety of everybody here. Politics should not bring violence."

The police chief added that nobody else is believed to have played a role in the attack. Electronics have been seized from the man's home.

The FBI is involved in the investigation.

A spokesman for Donald Trump's likely Democratic opponent in November, Kamala Harris, as well as Michigan's Democratic Governor Gretchen Whitmer, each released statements condemning political violence, according to the New York Times.

The shooting of the Republican White House candidate spurred bipartisan calls to lower the temperature of political rhetoric in the run-up to November's election, but the results have been mixed.

Last Friday police in Jupiter, Florida, arrested Michael Wiseman, 68, on suspicion of making online threats towards Trump and his running mate, Ohio Senator JD Vance, and their families.