Marvin Palencia, 38, of Hyattsville, was found guilty by a jury recently of first-degree murder while armed and other charges in the slaying of a man in a downtown office building, U.S. Attorney Ronald C. Machen Jr. announced in a statement.

Palencia, who was also found guilty of two gun charges and tempering with evidence, is scheduled to be sentenced on Oct. 11.

Authorities said that on Nov. 11, 2010, Palencia shot the victim, Jacobo Vazquez, 36, in the chest and the back of the head in the laundry room of an office building in the 100 block of Constitution Avenue NW. Both men worked there. Palencia was angry because Vazquez was in a relationship with his wife, from whom he was separated, but hoped to reconcile.

Prior to the murder, Palencia threatened Vazquez and warned him not to return to work. He then purchased a gun illegally and verified Vazquez’s work schedule. After killing Vazquez, Palencia put the body in a cardboard box, wrapped the box in duct tape, plastic, and a cord, and then dumped the body on the side of the road on Interstate 70 in Frederick County, according to the statement.

In his haste to wrap the box, however, Palencia unknowingly attached his work ID to it. He was arrested nine days after the killing.