A former soldier who said he became "addicted to killing" while serving in Iraq and Afghanistan has pleaded guilty but mentally ill to charges of raping and killing a Delaware woman.

Dwight L. Smith Jr., 28, entered the plea Friday at a hearing in Wilmington. He faces a mandatory sentence of life without parole when he is sentenced April 22.

Smith was charged with killing Marsha Lee of Wilmington while he was on leave from Fort Drum, New York, in December 2011.

Lee, 65, was abducted while walking her dog. Police said at the time that Smith had targeted Lee at random after deciding he wanted to kill somebody. Authorities said he hit Lee with his sport utility vehicle, raped her and beat her to death.