This is not what "die-hard fan" is supposed to mean.

A man killed his brother after the two got into a fight following the Cowboys loss to the Packers in last week's divisional round of the NFL playoffs, enabling Green Bay to reach the NFC Championship.

Robert Boyer, 46, fatally stabbed his brother, Justin, 40, a Cowboys fan who was visiting him in Las Vegas from North Dakota. According to KSNV:

Close friends of the brothers say the yelling was over the outcome of the Cowboys vs. Packers playoff game. A roommate separated the brothers but police say Justin came back and physically attacked his brother. That’s when police say Robert feared for his life and stabbed Justin."

Reports say there had been drinking going on prior to the fatal incident, as well. A roommate tried to intervene, but Justin, who reportedly suffered from a mental illness, would not let it go. According to police, Robert was acting in self-defense, while prosecutors will review the matter to see if they will pursue charges.

This isn't even the first time the Cowboys played a role in a family death, either, proving Dallas' fans can be pretty intense.