(CNN) A former Roman Catholic priest who spent decades on the run was sentenced to 30 years in federal prison for sexually abusing an altar boy in New Mexico.

At a sentencing hearing Friday, US District Judge Martha Vazquez described the case involving Arthur Perrault, 81, as the "worst case that I have ever handled and ever seen."

Perrault was convicted in April of seven federal counts for the early 1990s sexual assault of a 10-year-old boy, who was an altar boy at St. Bernadette's parish in Albuquerque. Authorities said Perrault abused the child in several places, including at a veteran's cemetery and a military base.

"I have to say, Mr. Perrault, that this is the worst case that I have ever handled and ever seen. I'm glad you're looking at me, because it is extremely difficult to speak to someone and to try to explain one's sentiments and have that person not give you the respect of looking at them," Judge Vazquez told the former priest in the Santa Fe federal courtroom.

"It was supposed to be your job to help, not destroy," she also told him.

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