Caddo, OK – A updated memorial honoring three heroic Oklahoma Highway Patrol troopers who were murdered in the line of duty forty years ago will be unveiled on Saturday, the agency said.

According to former Oklahoma Highway Patrol troopers, a humble memorial was established in the 1980’s just off of Choctaw and Court streets in memory of Troopers James Grimes, Billy Young, and Houston “Pappy” Summers, who were killed by escaped McAlester prison inmates on May 26, 1978, KXII reported.

“It’s Oklahoma Highway Patrol’s darkest day,” Lieutenant Scott Hampton told the news outlet. “It’s the day that we had many troopers [die] in the line of duty, on the Caddo-Kenefic manhunt.”

The troopers were searching for Claude Dennis and Michael Lancaster, both of whom had managed to escape from the prison.

Trooper Summers and Trooper Young stumbled upon the escapees on a dirt road near Kenefic, and were gunned down by the fugitives.

The men fled to Caddo, and ambushed Trooper Grimes and another unnamed officer in a residential neighborhood.

Trooper Grimes was fatally wounded in the attack.

“They haven’t been forgotten and…we all still think about their sacrifice,” Lt. Hampton told KXII.

The department received a donation of at least $16,000, which enabled them to add on to the original memorial site that was erected just feet from where Trooper Grimes was killed.

“The original monument will be here and we’ll have three individual monuments for each trooper and the slant in the middle will be a narrative as to what occurred,” said Tom Garner, who knew each of the slain deputies.

“[It’s] a wonderful effort to remember these men,” Garner added.