A Prince George’s County man was indicted Wednesday by a federal grand jury on charges that he took part in a 2008 home invasion robbery in Fairfax County in which three men were stabbed to death.

Delante Cook, 34, and his co-conspirators disguised themselves as police officers — wearing black outfits with the words “Police” and “SWAT” on them — when they entered a Springfield home Nov. 19, 2008, according to Fairfax police and an indictment in U.S. District Court in Alexandria. The robbers targeted the home because they thought the occupants were dealing marijuana, court papers say.

Brothers Ryan C. Strope, 26, and Terence J. Strope, 38, who rented the home on Moultrie Road in the Ravensworth Farm neighborhood, were fatally stabbed. Their friend, Andres A. Yelicie, 26, who was visiting, was also killed.

Cook, the first person arrested in connection with the crime, was charged with conspiracy and attempt to commit robbery.

The indictment alleges that other people were involved, including one man who has since died. Prosecutors, who said the investigation is ongoing, did not say who they think stabbed the men. No one has been charged with murder.

Neil H. MacBride, U.S. attorney for the Eastern District of Virginia, called the killings a “chilling and horrific crime.”

“This was a conspiracy that involved meticulous planning and masquerading as police officers to gain entry into homes they wanted to rob,” he said, noting that it ended with the “brutal stabbing deaths” of three men.

The killings shocked neighbors in the Fairfax community, and police and community leaders held a meeting to ease fears. More than 100 people attended.

Authorities said “recent evidence brought to the grand jury” gave them a break in the case.

In the two days before the robbery, Cook and another man, Jelani Slay, watched the home and planned the robbery, according to the five-page indictment.

On Nov. 19, 2008, Cook, Slay and other unidentified conspirators returned to the home dressed as law enforcement officials and armed with weapons, including knives, the indictment alleges.

“They wanted to rob them of cash, and they wanted to rob them of drugs,” MacBride said.

Authorities said two laptops and a cellphone were taken.

MacBride called the crime “a vicious, brutal, heinous stabbing” of three men. Fairfax Police Chief David Rohrer said that the brothers’ home might have been the target because of their alleged marijuana dealing but “these three men did not deserve to die.”

The Strope brothers are the sons of Christopher Strope, a retired Arlington County police officer and executive director of the Virginia Coalition of Police and Deputy Sheriffs.

Terence Strope ran a contracting business, Capitol Concrete Solutions. The brothers graduated from J.E.B. Stuart High School, where Ryan Strope played in the marching band.

Yelicie graduated from Paul VI Catholic High School in Fairfax and Virginia Commonwealth University. He worked at a credit union in the District.

If convicted, Cook faces a maximum of 40 years in prison. He was arrested Tuesday and made his initial appearance Wednesday in a federal courtroom in Alexandria. He is scheduled for a detention hearing Friday.

Slay was fatally shot in March 2009 by an off-duty D.C. police officer. Police said Slay, wearing a mask and brandishing a gun, tried to rob the officer.

Staff researcher Jennifer Jenkins contributed to this report.