Phillip Andrew Bauer battered the woman after their relationship ended and since then has vowed to kill her and two of her sisters if the family does not give him thousands of dollars he believes he is owed, court documents say.
The woman, who is not identified in the federal court documents, lives in constant and reasonable fear, prosecutors say. Even after Bauer was arrested in February 2011 he continued sending threatening letters.
"Right now I do nothing but hate your family and every day I think of revenge," he wrote in September 2011. The prosecutors' sentencing arguments contain excerpts of Bauer's messages.
Bauer, who is about 34 years old, pleaded guilty earlier this year to two counts of stalking and one count of mailing threatening communications to the woman and her family. He is to be sentenced on Aug. 8.
Government lawyers argue that the woman and her family will only be protected as long as Bauer is imprisoned.
"There is a very real danger (Bauer) will kill when he is released from prison and the only meaningful way to neutralize (Bauer) is for the court to sentence defendant to at least 10 years of incarceration," prosecutors say.
There are references in court documents to deportation proceedings but it's unclear where in Canada the man used to live, though one letter contains a reference to Vancouver.
Bauer is being represented by a public defender, who has until Monday to file his sentencing arguments. He asked for a time extension to respond to government arguments, which were filed Thursday. He did not respond to a request for comment.
Prosecutors say the woman has dropped out of college, relocated and changed her name but still lives in constant fear.
"Defendant is a dangerous bully who enjoys terrorizing innocent people," the prosecutors wrote in their sentencing memorandum.
"His contempt for the law and punishment does not deter him from acting on his impulses. Defendant feels that he has nothing to lose and thus he sees no downside in waging his campaign of terror against an innocent family."
One member of the family was too frightened to even submit a victim impact statement to the court, prosecutors say, but the woman's mother and stepfather describe the cloud of fear under which the whole family lives. Excerpts of their statements are in the prosecutors' sentencing arguments.
"My five stepdaughters and their spouses are frightened for themselves, their children and their siblings by the prospect of this self-described relentless maniac hunting them and have taken steps in and around their homes, workplaces and communities to protect themselves and those they love," the stepfather wrote.
The family asked the government not to tell the court what steps they've taken to protect themselves for fear Bauer will take them into consideration "when," not if, he hunts them down, prosecutors say.
The ex-fiancee's mother wrote that her grandchildren can't play in their own backyards and she hasn't seen her daughter smile since the threats began.
"Her self-confidence is gone," the mother wrote. "It makes it very difficult for her to plan out her life, when she's afraid she's going to be killed next month."
The threats are "chilling" to anyone who reads them, prosecutors say.
They began after the former couple got into an argument at their Arlington, Mass., home about their upcoming wedding and Bauer threatened to kill the woman if she left him. He said he would cut off her head if she contacted police and had him deported, according to an FBI affidavit, which says he was in the U.S. illegally.
The woman fled to her sister's home in California and got a restraining order against Bauer, but he wrote that neither restraining orders nor jail would stop him.
"You and your family are going to pay for what you did to me," Bauer wrote in April 2011, according to the prosecutors.
"If they don't pay me what is owed to me I am going to kill you and one of your sisters. If I can't find you I will kill two of your sisters and let you live with that guilt."
In the letter apparently written from behind bars Bauer said he sacrificed his youth so his ex-fiancee could go to school and become successful, and is now demanding $50,000 so he can get an education or he will kill her.
"I have sent multiple letters with no response," the prosecutors quote him as writing on another occasion. "I am getting angrier every day. Do you think some imaginary line on a map is going to stop me from coming?"
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