LANCASTER, Pa. -

A Lancaster County man has pleaded guilty to charges he robbed and assaulted three elderly Mennonite sisters.

Dereck Taylor Holt said in court Thursday that a prescription drug addiction is to blame and that the attack wasn't motivated by ethnic hatred.

Holt, 24, apologized and said he's "not a heartless being." He pleaded guilty to multiple counts of robbery, aggravated assault and other counts.

Holt pretended to be an insurance salesman to get inside the Clay Township home in December, then bound the victims, hit them with a stun gun and sprayed the home with household chemicals. Investigators initially believed it was a targeted crime, but charges of ethnic intimidation were later dropped.

Sentencing isn't expected for several months.