The letters and e-mails, which started coming in September 2006, continued even after Ajemian was asked to stop and were "intended to cause annoyance and alarm," Thompson said.

"I want a public confession before I ever consider giving you absolution or a spot on your couch," wrote Ajemian, who signed the notes "Padre," Thompson said.

Ajemian also has been in contact with O'Brien's parents, Thompson said.

A telephone message left Wednesday night at St. Mary-St. Catherine of Siena Church in Boston, which Ajemian gave as his address, was not immediately returned.

O'Brien is not commenting, an NBC spokesman said.

The Boston Archdiocese said in a statement that Ajemian had been placed on leave and was no longer allowed to minister publicly. O'Brien has participated in fundraising activities for the archdiocese.

The priest and the late-night host may have attended Harvard University at the same time.

O'Brien graduated in 1985, and Ajemian graduated from high school in 1979 before attending the Ivy League school, according to an alumni magazine published by his high school.

The priest could face up to a year in prison if convicted of aggravated harassment and stalking.