A man called Markey's congressional office the day before the Sunday vote and told an assistant that "[you] better hope I don’t run into you in a dark alley with a knife, a club or a gun," MSNBC reported Wednesday.

The FBI is investigating threats against the lawmakers after acts of vandalism that included shattered windows at four Democratic offices in New York, Arizona and Kansas and a severed gas line at the Virginia home of a Democratic lawmaker’s brother, MSNBC reported.

An aid to Markey called Fort Collins police Sunday afternoon requesting increased patrols around her unoccupied home out of concern it might be vandalized, “because of her health care vote” later that day, Sgt. Joel Tower told TheDenverChannel.com Wednesday night.

“There was no specifics given to use about why they expected that (vandalism) or if they'd received any threats," Tower said. Markey’s aid told police that no one was staying at the home this week.

Police did increase patrols around Markey’s home in Fort Collins’ Old Town neighborhood, but there hasn’t been any vandalism or protests there in the wake of the health care bill’s passage, Tower said.

Northern Colorado Tea Party Director Lesley Hollywood issued a statement Wednesday night saying the group's members "are saddened tonight to hear of threats made upon Democratic lawmakers in response to the passing their recent health insurance reform legislation, specifically 4th Congressional District Rep. Betsy Markey."

"Although it does not appear that these threats stemmed from those within Colorado's Tea Party movement, organizers and members alike are firmly denouncing any acts of intimidation or threat," Hollywood said.

"Although many are frustrated by the passage of such controversial legislation, threats are absolutely not acceptable in any form, to any lawmaker, of any party." Hollywood added. "As a member of the Tea Party state leadership team, I can assure you that myself and my colleagues will take immediate action if any of these allegations are discovered to be connected to our organizations."

House Majority Leader Steny Hoyer said FBI and Capitol Police briefed Democrats on how to handle perceived security threats.

The FBI issued a statement saying that U.S. Capitol Police and other law enforcement agencies are trying to identify and bring to justice those responsible.

Democrats weren't the only politicians who had scary incidents.

Virginia Republican Rep. Eric Cantor revealed this week that a bullet hit the window of his Richmond, Va., campaign office early Tuesday morning.

At a news conference Thursday, Cantor angrily lashed out at Democratic leaders for their handling of reported threats against members of Congress, the Washington Post reported.

"I've received threats since I assumed elected office, not only because of my position but also because I'm Jewish,'' said Cantor, who is the third-ranking House Republican. "I've never blamed anyone in this body for that, period. Any suggestion that a leader in this body would incite threats or acts against other members is akin to saying that I would endanger myself, my wife or my children."

Richmond police said Friday that the bullet that hit Cantor's office was a random shot.

"It is a stray bullet as part of random gunfire,'' Richmond police spokesman Gene Lepley told the Post. Police said they have no suspects.

Police said the bullet struck with enough force to break the window, but did not penetrate the blinds, the Post reported. It landed on the floor about a foot from the window.

Concern about possible violence rose Wednesday after the discovery of the slashed gas line leading to a propane tank at the home of Bo Perriello was found Tuesday, one day after tea party activists posted the address online and suggested that opponents of the reform bill should “express their thanks” to the man's brother, Rep. Tom Perriello, D-Va, MSNBC reported.

There is speculation that conservative activists believed they were posting Rep. Perriello’s address after suggesting in Web postings that those who disagreed with the Democratic lawmaker’s vote should "drop by" to make their opposition clear." MSNBC reported.

House Republican leader John Boehner of Ohio issued a statement that while many Americans are angry over the bill's passage, "violence and threats are unacceptable."

"That's not the American way," Boehner said. "We need to take that anger and channel it into positive change."