DOYLESTOWN — The scene repeats again and again in Aimee King’s mind: She sees her son Mark Sturgis in his last moments on an upper Bucks County farm last July.

Sturgis’ mother and the parents of three other young men arrived in the morning at the county courthouse expecting closure in one of the region’s more haunting crimes: the gruesome murders and burial of their sons on that remote Solebury Township tract.

They didn’t get it. Hours after the lead defendant, Cosmo DiNardo, pleaded guilty and was sentenced to four life terms in prison for the killings, his cousin and alleged co-conspirator Sean Kratz balked at his own chance for a plea deal.

Kratz’s last-minute change of heart not only stunned the families, but it also appeared to shock his attorneys.

And it left prosecutors pledging to move ahead with a death penalty trial at which DiNardo could become a central witness.

“We’re undaunted as we continue to seek justice,” District Attorney Matthew Weintraub said.

The unexpected turn of events came after DiNardo, 21, of Bensalem, had accepted responsibility for his part in the July deaths of Sturgis, Thomas C. Meo, Dean A. Finocchiaro and Jimi Patrick.

On three separate trips, he lured the young men to his family’s property with a pledge to sell them marijuana, but instead shot them and buried them in makeshift graves.

Their disappearances drew a national spotlight.