RIVERTON, Wyo. (AP) — Prosecutors have filed a first-degree murder charge against a Riverton man accused of killing his former roommate with a claw hammer during an argument.

Florin Brandon Wyatt, 27, was initially charged with second-degree murder in the death of 56-year-old Keith Stephenson, whose body was found in a home Sunday morning. That charge was changed to first-degree murder because prosecutors believe the slaying was premeditated.

According to an affidavit, Wyatt told investigators he and Stephenson had been arguing March 3 about the Denver Broncos when he retrieved and hid a hammer. Wyatt says Stephenson tried to hit him during an argument later than night, so he grabbed the hammer and struck the man in the head.

It's unclear if he has hired an attorney who can speak on his behalf.