An investigation into a threatening letter sent anonymously to the home of Democratic Reform Minister Pierre Poilievre – the man spearheading the controversial Fair Elections Act – has led RCMP to question at least one other letter-writer who wrote and signed his own message to the minister criticizing the bill.

It's unclear how many letters, and the personal information of those who sent them, have been turned over to the RCMP by government after the initial threat to Mr. Poilievre was reported.

(What is the Fair Elections Act? Read The Globe and Mail's easy explanation)

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But Barry Epstein, a 73-year-old retiree from Manitoulin Island in Ontario, said he was visited on April 11 by RCMP after writing an April 9 e-mail to Mr. Poilievre about the bill. The e-mail is very harshly worded – more than any he'd written before, Mr. Epstein says – and challenges Mr. Poilievre to come to an all-candidates meeting before next year's election.

"I look forward to lining up at the microphone and telling you in person what kinds of a pathetic excuse for a human being you really are. Canadians are on to you now. Your day in the sun is coming to an end," Mr. Epstein wrote, signing "yours angrily" with his name and address. The e-mail also compares Mr. Poilievre to two Nazi officials.

Mr. Epstein said RCMP visited him about his e-mail and interviewed him, saying they were following up on another letter, sent anonymously by mail and around the same time, with death threats to Mr. Poilievre. According to Mr. Epstein, police told him that he and three other letter-writers from the same Sudbury region were being questioned. He wasn't arrested and doesn't believe he's suspected of any wrongdoing.

The RCMP didn't confirm or deny any investigation. A spokeswoman for the minister declined comment, calling it a "security matter," as did the Prime Minister's Office. "Questions related to an RCMP investigation should be referred to the RCMP," PMO spokesman Carl Vallée said.

The anonymous, threatening letter appears to have led RCMP to question others who wrote to Mr. Poilievre. Mr. Epstein said he was fingerprinted by police, only after consenting, who said they had pulled fingerprints from the envelope sent to Mr. Poilievre. "It wasn't an unpleasant or intrusive experience. The officers who were here were very professional, and I didn't feel I was under threat or pressure," Mr. Epstein said in an interview.

The bill has proven deeply divisive, with a broad range of non-partisan experts calling for significant changes. Some groups have led letter-writing campaigns against the bill, which Mr. Epstein opposes. "I have very strong feelings, of course, like other people, that it's a threat to our democracy and our rights to vote freely in this country," he said.

RCMP in Ottawa, and in the division overseeing the Ontario region, declined comment. "I can say that our RCMP investigators routinely speak with persons in the course of their duties to determine the substance of allegations, but I don't have any comment on that specifically," said RCMP Sergeant Richard Rollings, a spokesman for the Ontario division.