HARRISBURG, Pa. (AP) — A man imprisoned since 2001 for attacking educators and students in a Pennsylvania elementary school with a machete, wounding 14, has died in prison.

William Stankewicz died Monday, Pennsylvania prison officials said. He was 78.

Stankewicz was found unresponsive in his cell at the State Correctional Institution at Dallas, the prison warden said in a statement. Authorities did not release a cause of death and said his death will be investigated.

Stankewicz was serving a 132- to 264-year sentence for the attack on North Hopewell-Winterstown Elementary School near York, about 75 miles (120 kilometers) west of Philadelphia. The wounded included 11 kindergarten students.

Principal Norina Bentzel was the most seriously hurt, suffering severe cuts and a broken arm while helping wrestle Stankewicz to the ground.

In court, Stankewicz told the judge he committed the attack because he was angry about his divorce from his Russian-born ex-wife and her allegations that he molested her daughters. Stankewicz said she used him to get to America and then made the allegations to remain in the country.

Stankewicz, of Johnson City, Tennessee, said he attacked the elementary school because he could not find his ex-wife’s home.

Before the attack, Stankewicz had threatened to kill his ex-wife and her daughters. After he unsuccessfully sought to get her deported, he threatened immigration officials and a Pennsylvania congressman. He served two years in federal prison for the threats.