Oklahoma: death row inmate Gary Welch has been executed - first in U.S. in 2012.

An Oklahoma inmate has been put to death for killing a man during a knife fight nearly two decades ago, marking the nation's first execution this year.

Forty-nine-year-old Gary Roland Welch was given a lethal injection Thursday at the state penitentiary in McAlester for the fatal stabbing of 35-year-old Robert Hardcastle in Miami, Okla.

He was pronounced dead at 6:10 p.m.

Minutes before the drugs were administered, other death row inmates could be heard banging on their cell walls, and Welch paid tribute to them during his final statement.

Nearly three weeks ago, Welch attempted suicide by slitting his throat with a smuggled shaving razor.

Prison officials and Welch's court-appointed attorney insisted he was sane and understood his fate.

Welch maintained that he only killed Hardcastle in self-defense, krmg.com reported.