(CNN) A millionaire stock trader was sentenced to nine years in prison Monday in the death of a worker he'd hired to dig tunnels beneath his house in suburban Washington, DC, as protection from potential North Korean missile strikes.

Daniel Beckwitt, 28, had been found guilty in April of second-degree murder and involuntary manslaughter in the death of Askia Khafra, 21, who was found "naked" and "charred" in the burnt-out basement of the Bethesda, Maryland, residence.

Dia Khafra, father of Askia Khafra, holds a photo of his son in his Silver Spring, Maryland, home.

During the two-week trial, prosecutors described how Beckwitt hired Khafra to build the complex of bunker-like tunnels in case of an attack by North Korea, said Ramón V. Korionoff, a spokesman for the Montgomery County State's Attorney's Office.

Beckwitt would pick up Khafra from his home in Silver Spring, Maryland, outside of Washington, and require Khafra to wear darkened, blackout glasses that prevented Khafra from seeing where he was being driven to, according to a statement of charges from the Montgomery County District Court.

The document also says that once Beckwitt picked up Khafra, he told him they'd be going to an "undisclosed location in Virginia," but Beckwitt would instead drive to his house in Bethesda.

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