A Winthrop man who several years ago pleaded guilty to setting a fire at the town’s public library is going to jail on unrelated charges. Zachary Lowe was ordered by a judge this week to spend six months of a three-year sentence behind bars for stealing prescription medicine from his grandmother, violating conditions of release and assaulting his sister after she told him to leave her West Gardiner home. Lowe, then 16, started a fire at the Winthrop public library by pushing a lit paper towel roll through a basement window. The blaze caused about $160,000 in damage and Lowe was sent to a youth detention facility. The Kennebec Journal, reports that Lowe’s attorney says his client is “grown up” and committed to taking care of his drug problem.