A Pennsylvania prosecutor says he'll seek the death penalty against a man accused of sexually assaulting and killing a sixth-grade math teacher during a burglary at her home.

Lancaster County District Attorney Craig Stedman said Friday that 25-year-old Thomas Moore tortured Nicole Mathewson and killed her after committing multiple felonies.

He says those factors warrant capital punishment.

Moore's 16-year-old co-defendant won't face the death penalty.

Moore and the teen are charged with homicide, involuntary deviate sexual intercourse, burglary, robbery and other offenses in the Dec. 15 killing in Lancaster.

Moore's lawyer has said his client isn't responsible for Mathewson's death. He didn't immediately return a message Friday.

Mathewson taught at Brownstown Elementary school. Police say she'd been home alone, and Moore and the teen didn't know her.