A former St. Paul man arrested in October with a "hit list," a double-edged boot knife, a loaded gun and more than 200 rounds of ammunition was sentenced Thursday to six years in prison for stalking his ex-wife and her supporters.

Michael J. Mangan's attorney, Tyler Bliss, pleaded for probation. But Sarah Cory, assistant Ramsey County attorney, urged the court to send Mangan away for 6½ years, double the guideline sentence, due to aggravating factors.

Mangan, 43, pleaded guilty in May to three counts of aggravated stalking. Eight other counts of stalking and terroristic threats were ­dismissed as part of the plea deal.

Ramsey County District Judge Rosanne Nathanson handed down a stiff sentence, she said, because of the "very broad and deep" damage caused by Mangan's actions.

"There was extraordinary planning, and there was what can only be called a 'hit list,' " Nathanson said.

Mangan, a Marine, terrorized his ex-wife and her supporters from the time of their divorce in December 2011 until his arrest on Oct. 4, Cory said before sentencing. He followed his victims and learned their routines, researched ambush techniques and was ready to commit murder.

"The defendant's actions went well beyond stalking somebody," Cory said. "He prepared himself to destroy his ex-wife's life."

Mangan's sister and brother-in-law reported him to police after he revealed some of his plans to his brother-in-law in September. The brother-in-law told police that Mangan had papers diagraming the ex-wife's apartment complex and workplace. The two have four children.

Mangan was arrested during a traffic stop, during which time the weapons and ammunition were discovered. Sealed letters addressed to 11 addresses were found in his apartment along with instructions for his girlfriend to send them once he was "gone."

"Your mother did this," he wrote in a letter to his children. "… I took the only action I had left in my power and that was to remove the problem."

Bliss said that he would not contest that Mangan's actions caused deep fear in his victims. But, he said, Mangan would not have killed anyone.

Mangan posted bail, immediately moved to Florida, enrolled in school and started a business, Bliss said. Mangan deserved a chance to restart his life on probation, he argued.

"I truly am sorry," Mangan said when given an opportunity to talk. "My life fell apart, and I found myself completely connected to that anger."

Nathanson was unmoved. The judge had read confidential victim impact statements that were not read aloud in court and noted that some victims made "significant" life changes because of Mangan.

Mangan acted with "disproportionate and even dangerous" response to his divorce, the judge said, adding that it was clear from his letters that he had intended to kill others and end up dead himself.

"These letters presumed that the plans would proceed and that Mr. Mangan and others would be deceased," Nathanson said.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib