DENVER (AP) - The U.S. Supreme Court has rejected the death sentence appeal of Nathan Dunlap, who killed four people at a Colorado Chuck E. Cheese restaurant in 1993.

Dunlap was sentenced to die for killing four people in 1993.

He is Colorado's longest-serving death-row inmate, and could become the first inmate executed in the state since 1995.

According to the Denver Post, the ruling ends the last appeal Dunlap is guaranteed under the law.

Dunlap may file further appeals, but they are not certain to delay his execution. An attorney for Dunlap declined to comment.