Four people pleaded guilty Thursday to their roles in the home invasion robbery of a developer who was tied up and beaten in his luxury penthouse at an exclusive apartment building overlooking the Hudson River.

Jorge Valencia, 48, who worked as a superintendent at the St. Moritz building in Edgewater, admitted to hatching the scheme to steal diamonds, gems, gold bars, cash and jewelry valued at more than $3 million in 2013. He pleaded guilty to armed robbery, conspiracy to commit kidnapping and hindering his apprehension by fleeing to Boston.

Alexander Suarez, 21, Adonis Sepulveda, 32, and Ramona Mercado-Vasquez also pleaded guilty in the case. Sepulveda and Mercado-Vasquez lived at the building. 

Bergen County Assistant Prosecutor David Calviello called it an "inside job," and told The Record newspaper that the defendants "targeted a multimillionaire who kept large sums of expensive property and cash on hand."

Valencia told the judge he had access to a key to the victim's apartment. The robbers ousted the victim from his bed, bound and blindfolded him and put a gun to his head, authorities said. Complying with their demands, the victim called the night doorman to come up to his apartment, where he also was bound and threatened with a gun to his head, authorities said.

The doorman had been lured away so the robbers could gain access to the building's security camera system. They removed digital recording devices, but missed one unit in an adjacent room.

Sentencing has been scheduled for Nov. 13.