BILLINGS, Mont. (AP) — Billings police say a 19-year-old man killed his great-grandmother, apparently for her television and car.

Chief Rich St. John said Monday that Denver police had arrested Robert A. Thompson on Saturday morning in the killing of 77-year-old Shirley Lawrence.

Her body was found Friday when a relative stopped to check on her at her Billings home.

An autopsy concluded she died of blunt-force trauma and multiple stab wounds.

The Billings Gazette reports Thompson had been staying with Lawrence.

St. John says Denver police found Thompson and three juvenile males in Lawrence's car.

The police chief says Thompson eventually admitted to killing Lawrence.

It was not immediately clear if he had an attorney.

St. John says the motive appears to be for the television and car, although police continue to investigate.