Maryland prosecutors have ruled out charges against the police involved in the slaying of Duncan Socrates Lemp, the so-called Boogaloo martyr, whose family said he was asleep alongside his pregnant girlfriend when SWAT officers opened fire outside the house.

The family's version of events directly contradicts the Montgomery County Police Department, which said Lemp confronted officers with a rifle during a no-knock raid at the family home at 4:30 a.m. on March 12.

Howard County State’s Attorney Rich Gibson Jr. told Lemp’s family Thursday that the use of deadly force was justified, Rene Sandler, a lawyer for the relatives, told the Associated Press.

Howard and Montgomery counties have an agreement where their prosecutors review each other’s police-involved shooting cases.

This 2019 photo shows Duncan Lemp in Venice, Italy. Maryland prosecutors aren't charging police officers in the shooting death of Duncan Lemp, whose family says he was sleeping in his bed next to his girlfriend when police opened fire. Family attorney Rene Sandler told The Associated Press that Howard County State’s Attorney Rich Gibson Jr. informed the parents and girlfriend of 21-year-old Duncan Lemp of the decision Dec. 31. (Mercedes Lemp via AP)

This 2019 photo shows Duncan Lemp in Venice, Italy. Maryland prosecutors aren't charging police officers in the shooting death of Duncan Lemp, whose family says he was sleeping in his bed next to his girlfriend when police opened fire. Family attorney Rene Sandler told The Associated Press that Howard County State’s Attorney Rich Gibson Jr. informed the parents and girlfriend of 21-year-old Duncan Lemp of the decision Dec. 31. (Mercedes Lemp via AP)

"In reaching their conclusion, they had to, unfortunately, ignore very important facts from eyewitnesses," Sandler said, adding that Lemp’s parents were "extremely disappointed" and planned to file lawsuits.

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Gibson’s office did not immediately respond to a Fox News request for comment.

Lemp’s girlfriend gave birth to the couple’s son in October.

Mercedes Lemp poses for The Associated Press by holding her 2-day-old grandson near portraits of the newborn's father, Duncan Lemp, Friday, Oct. 16, 2020, in Frederick, Md. The Lemp's are dealing with the death of their Duncan Lemp, who was shot at their home in Potomac, Md., during a no-knock police raid on March 12, 2020. Lemp's family have said through their attorney that, based on an eyewitness, they believe Lemp was shot without warning while he was asleep. (AP Photo/Julio Cortez)

Mercedes Lemp poses for The Associated Press by holding her 2-day-old grandson near portraits of the newborn's father, Duncan Lemp, Friday, Oct. 16, 2020, in Frederick, Md. The Lemp's are dealing with the death of their Duncan Lemp, who was shot at their home in Potomac, Md., during a no-knock police raid on March 12, 2020. Lemp's family have said through their attorney that, based on an eyewitness, they believe Lemp was shot without warning while he was asleep. (AP Photo/Julio Cortez)

In response to Lemp’s slaying, armed adherents to the loosely defined Boogaloo movement -- an anti-government group that expects a second "civil war" to be fought in the U.S. -- have hailed Lemp as a martyr. Some have given his name as their own when approached by media or law enforcement during protests around the country.

The so-called Boogaloo Bois are known for showing up at protests in Hawaiian shirts and protective vests while carrying firearms. The name was taken from the 1980s movie "Breakin' 2: Electric Boogaloo." The Hawaiian shirts are worn because "boogaloo" sounds somewhat like "big luau." Members also sometimes wear patches that depict a "big igloo."

Lemp was a 21-year-old computer programmer known to post online to Boogaloo-themed forums and social media groups. Investigators said he was suspected of belonging to a militia, and manufacturing and selling ghost guns, untraceable firearms without serial numbers, according to court documents obtained by the Washington Post.

His parents have disputed characterizations of their son as a member of a radical movement or as a threat to police.

Matt Lemp, left, and his wife, Mercedes Lemp, pose for the Associated Press in their home, Oct. 16, in Frederick, Md. (AP Photo/Julio Cortez)

Matt Lemp, left, and his wife, Mercedes Lemp, pose for the Associated Press in their home, Oct. 16, in Frederick, Md. (AP Photo/Julio Cortez)

The case also attracted the attention of Judicial Watch, which sued Montgomery police over the summer for access to bodycam footage of the incident.

But investigators had no access to bodycam video because Montgomery County policy excludes frontline tactical officers from wearing them, the Post reported Thursday.

Lemp had a criminal record that prevented him from owning firearms until his 30th birthday, but police said they found three rifles and two handguns during the raid.

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Other followers of the Boogaloo ideology have been linked to violent attacks around the country – including former Air Force Sgt. Steven Carrillo, who is accused of killing a federal officer standing guard outside an Oakland courthouse and later a California deputy during a statewide manhunt.

The Justice Department named the Boogaloos and Antifa in a memo earlier this year as two groups that have promoted violence and rioting during nationwide protests.

The Associated Press contributed to this report.