Police have arrested the ex-boyfriend of Jenni-Lyn Watson, whose body was found in a storage shed near Clay Central Park, N.Y., Saturday afternoon. Steven Pieper, 21, has been charged with second-degree murder.

Pieper pled not guilty Saturday night to killing Watson and dumping her body in the park.

A prosecutor tells the Syracuse Post-Standard that Pieper, of Liverpool, N.Y., was held without bail because of the seriousness of the charge. It was not immediately clear if Pieper had a lawyer.

Watson and Pieper had an on-and-off relationship over an 18-month period, according to Onondaga County District Attorney William Fitzpatrick, WSYR-TV reports.

The arrest comes hours after Watson's body was found in Clay Central Park, where the search has focused since she disappeared on Nov. 19.

Watson's family has been notified and will identify the remains. An autopsy is planned for Sunday, WSYR-TV reports.

A friend of Watson's, who spoke to FoxNews.com on condition of anonymity, said the young woman had recently broken off an engagement.

"The break-up didn't go as cordially as it should have," the friend said.

Eden Mishler, a dance major who had met Watson three years ago during her freshman year at Mercyhurst College, told The Associated Press that she had met Pieper several times but didn't know him that well.

"She would talk to us, just saying, after they broke up, that he was trying to contact her and friend request her on Facebook," the 21-year-old Mishler said. "She was avoiding him."

But she said the two had a rocky relationship, and there was some jealousy. Nevertheless, Mishler thought he cared for her.

Watson, 20, disappeared a day after returning home to Clay for Thanksgiving break. Undersheriff Warren Darby said Friday that more than 100 people were searching for her. 

He said the search expanded from 600 acres to 1,200 acres. Watson -- 5-feet 2 inches tall and 100 lbs. with dirty blond hair and brown eyes -- was an accomplished ballerina and dance major at Mercyhurst College in Erie, Pa.

Friends describe Watson as a "sweetheart" who excelled in ballet for 16 years, performing with the prestigious Moscow Ballet.

The Associated Press contributed to this report.