Updated: September 10, 2012, 3:34 PM CST

PHILADELPHIA (AP) — A woman has been convicted of fatally shooting two colleagues at a Philadelphia food plant.

A judge on Monday also found 45-year-old Yvonne Hiller guilty of one count of attempted murder for wounding a third co-worker.

Hiller will serve a mandatory life term for the two first-degree murder convictions.

Prosecutors had agreed not to seek the death penalty. In return, Hiller waived her right to a jury trial and agreed not to use an insanity defense.

Police say she was suspended from Kraft Foods after a confrontation in September 2010, left the plant and got a gun, and returned minutes later.

The judge rejected Hiller's claim of self-defense, in which she mistakenly believed co-workers were spraying her with chemicals that smelled like deer urine.