A "Kill Your Local Trump Supporter" graffiti was spray-painted in white letters 20 feet long on School of the Museum of Fine Arts property on St. Alphonsus Street.

It's unclear when the graffiti first appeared on the side of a gray building in Mission Hill that houses studio and exhibition space for the school. The message faced the parking lot of an adjacent building, and was visible from a sidewalk. It was painted over late this morning.

Sam Lovett-Perkins, 21, a nursing major at Northeastern University, said he walks by the building daily on his way home from classes, but noticed the graffiti for the first time this morning.

"I think it's ridiculous. It's violent and unnecessary," said Lovett-Perkins, a Democrat and Hillary Clinton supporter. "I think it's overkill on how we view each other as people. It's outrageous where we've gotten to as a nation."

Boston police could not immediately be reached for comment.

State Rep. Geoff Diehl (R-Whitman), state campaign co-chair, said, "To actually advocate for killing someone is beyond the pale."

But Diehl told the Herald he's confident not even "hell or high water" will deter Trump supporters from voting Tuesday.

"I don't think there's anybody not planning to go because of safety concerns," Diehl said. "One random act of a threat hopefully doesn't translate into anything else."

It's unclear who painted the graffiti, but Diehl said, "It's been a disturbing trend in this presidential cycle that there's been people recruited from the left to attack Trump rallies and now we're seeing what is turning into desperation on the side of the Clinton campaign to bully Trump voters into not coming out on Tuesday.

"All they have is attacks on Donald Trump," he said, "and no change in policy for getting America back on track."

Several Trump rallies over the summer were targeted by rioting protesters.

Last night, Trump was rushed off a campaign stage by his security detail in Reno, Nev., last night when someone in the crowd yelled, "Gun!" according to the U.S. Secret Service.

One individual was detained, but later released. No weapon was found, the Secret Service said.

Of the graffiti incident in Boston, Lovett-Perkins said although Clinton has his vote, he bristled at the threat to Trump backers.

"I think everyone has an equal right to live happy and free," he said, "and this is definitely against that."