A man who attacked a Pennsylvania elementary school with a machete was found dead in his prison cell on Monday morning after serving 22 years of a 132- to 264-year sentence, according to authorities. William Stankewicz was 78. In Feb. 2001, he walked into North Hopewell-Winterstown Elementary School with a 2-foot-long machete, wounding 11 kindergarten students, two teachers, and the principal before he was eventually wrestled to the ground. The principal, Norina Bentzel, was the most seriously injured in the attack, breaking her arm and suffering serious cuts while helping to subdue Stankewicz. He later pleaded no contest to charges of attempted murder, aggravated assault, and possessing weapons on school grounds. He told the court he had carried out the plot because he was angry about his separation from his wife, who he accused of using him to obtain legal residency in the United States, according to the Associated Press. Pennsylvania State Police are expected to investigate Stankewicz’s death, prison officials said. An official cause of death will be determined by the Luzerne County Coroner's Office.