A Maryland SWAT officer will not be charged in the fatal shooting of 21-year-old Duncan Lemp during a predawn weapons raid in Potomac that became part of the nationwide debate over no-knock warrants, prosecutors said in a 17-page report released Thursday.

The Montgomery County Police officer was legally justified when he fired five rounds at Lemp through a broken bedroom window in March because, prosecutors said, Lemp had ignored commands to raise his hands, gotten out of bed, grabbed an assault-style rifle and pointed it toward the officer.

“Police! Show me your hands!” the officer yelled, according to prosecutors, followed by pleas to surrender: “Don’t do it! Don’t do it!”

A gifted computer programmer who lived in his parents’ home, Lemp had caught the attention of police after they received tips that he illegally possessed weapons and had written online that he was an active member of a self-proclaimed militia, the report said. They also suspected that Lemp had been illegally manufacturing and selling “ghost guns,” which don’t have serial numbers and can’t be traced.

The front-line SWAT officers in the raid weren’t wearing body cameras. One of them, the officer who fired his weapon through the window, did so as other SWAT members stormed through the house after battering through the front door. Their raid was complicated because earlier surveillance of the home showed that Lemp had rigged a different exterior door — leading to his bedroom — with a booby trap designed to explode a shotgun shell into the face of an intruder, according to prosecutors’ findings.

They also asserted that private text messages Lemp had written in the months before the shooting revealed he expected the police to raid his bedroom. He wrote about the need to reinforce the interior door to his bedroom to withstand a battering ram’s blow. And he indicated he was ready to shoot when officers came.

“I’ve accepted the inevitability and made peace with my demise,” he wrote to a friend earlier in 2020, according to the report. “At least I’ll go down kicking.”

After the raid, the report said, police recovered from Lemp’s bedroom at least 50 boxes of ammunition, a ballistics vest, three assault-style rifles, a handgun on his nightstand and parts for more booby traps.

“The threat caused by Duncan Lemp retrieving a rifle and pointing it at the officer, coupled with Lemp’s apparent refusal to obey lawful commands, justified the shooting officer’s use of deadly force,” prosecutors concluded in the report, which relied on the use of a grand jury and several witness interviews.

Lemp’s family members have long held that the police exaggerated the threat he posed. His family has said police obtained a no-knock warrant based on flimsy evidence, opened fire on him while he was still asleep, and then burst into his room and stomped on his neck — assertions contradicted by the report.

Lemp was struck by all five founds in front of his girlfriend.

Attorneys for Lemp’s family and his girlfriend blasted the report as incomplete and misleading. The exoneration of the officer, they said, has only caused more anguish to their clients.

“Their hearts are broken at losing Duncan,” said Cary Hansel, who represents Lemp’s girlfriend. “Their hearts are broken again by the lack of justice in this report.”

Rene Sandler, who represents Lemp’s mother, father and brother, said that if police had questions about Lemp’s guns, they could have called him on the phone, knocked on his door during the daytime or pulled him over in traffic.

“Duncan had never been violent in the past. He wasn’t a threat to anyone,” she said.

Both lawyers called on Montgomery State’s Attorney John McCarthy to release all of the testimony and evidence presented to the grand jury.

The report expanded beyond the specifics of the shooting, breaking down how and why police made such an aggressive entrance into the Lemps’ one-story, ranch-style home. The report also addressed two broader policy issues — no-knock warrants and body-worn cameras — that are part of police accountability discussions nationwide and in Montgomery County.

“The reasons for the ‘no-knock’ provision was due to Lemp being ‘anti-government,’ ‘anti-police,’ currently in possession of body armor, and an active member of the Three Percenters,” the report said, referencing what it called a far-right militia movement. “Additionally, police had viewed several videos showing Lemp handling and shooting firearms. The police felt that knocking and announcing their presence would put the officers in serious danger if Lemp decided to resist his arrest.”

The report also said the Lemp home was the subject of an earlier police raid, in 2016, but didn’t say what precipitated it. McCarthy and Sandler declined to comment on it.

The nine-month investigation was conducted in the absence of useful police video recordings. Montgomery County has a policy of not equipping front-line SWAT officers with body cameras, according to department records. One SWAT team member did have a body-worn camera, according to the report, but it was not activated until after the raid was over.

Anti-government extremists around the country, to whom Lemp has become a beloved martyr, have also questioned the shooting. The lack of body camera footage is likely to fuel speculation from them and others.

“#DuncanLemp can be an inspiration,” a Lemp supporter wrote on Twitter recently. “Murdered by the state.”

Since the shooting, Montgomery police commanders have acknowledged the limits of their policy on body cameras, which for years have been required for uniformed patrol officers. Police Chief Marcus Jones said Thursday that his department will expand their use to front-line SWAT officers early next year.

McCarthy applauded the department’s decision, saying the “exception for SWAT officers never made sense to me.”

“Had body camera footage existed, this case could have been done much quicker,” said McCarthy, who stood by the findings of the report and disagreed with the family’s assertions that it was incomplete.

Police commanders this year have defended their use of no-knock warrants, which they have conducted about twice a week in recent years. In July, police officials pushed back against efforts to abolish or curtail no-knock warrants — helping carve out a wide range of investigations for which they could still be used. In legislative testimony over the summer, Jones said that in 40 years of performing no-knock warrants, the county SWAT team had been involved in only three shootings, and the Lemp raid was the first that turned fatal.

“That speaks volumes to the tactics and the training that these officers go through consistently,” Jones said.

Citing a barrage of death threats the case has evoked from extremists, the police department repeatedly declined to identify the officer who killed Lemp, counter to its long-standing policy for officers involved in fatal shootings. The report also did not identify the officer.

As with all such shootings in Montgomery County, the case was first investigated by the department’s homicide division. It was supervised by prosecutors one county to the north, Howard County, following a policy designed to lend independence.

Lacking much body camera video, prosecutors drew largely on the recollections of the shooting officer, Lemp’s girlfriend and forensic evidence from the bedroom.

When Montgomery County implemented its body-worn camera program in 2016 amid national calls for increased police accountability, the department mandated them for patrol officers, according to police department documents. SWAT officers were exempt, as officials feared that recordings released to the public could reveal raid tactics and endanger officers and future operations.

The notion that body camera videos will reveal tactics has historically been a concern to SWAT officers, but it’s one that’s fading, said Thor Eells, executive director of the National Tactical Officers Association. The footage that gets released, he says, tends to be from individual SWAT officers, revealing only a small part of the larger raid strategy. The trade-off — showing the public how controversial parts of raids unfolded — serves SWAT teams better in the long run, according to Eells.

“You’re not exactly giving up the crown jewels,” he said. “And in the vast majority of these cases, video exonerates allegations against the officers.”

In 2018, Montgomery police extended body camera requirements to SWAT “team leaders,” who are often positioned in the rear of raids and less likely to use force compared with front-line tactical officers. Team leaders are required to activate cameras “immediately preceding the entry of the target location,” according to written agency directives, but are allowed to avoid recording “when possible and in a manner which does not compromise the safety” of the team.

In February, according to the prosecutors’ findings, Montgomery police received information about Lemp from a confidential source, who said that Lemp was part of a self-identified militia group, that he had a bulletproof vest and that he’d made “anti-police” statements.

Detectives looked into Lemp and his online presence. Instagram postings showed him shooting different types of guns, including what investigators thought was an assault rifle banned in Maryland, the report said. Police learned that Lemp had installed a booby trap on the exterior door leading into his bedroom, according to prosecutors.

Lemp had a juvenile record, police had said earlier, which prohibited him from owning firearms until he was 30.

About 4:30 a.m. on March 12, at least 12 officers drove down Saint James Road, stopping near Lemp’s house.

Many of the SWAT officers approached the front door, carrying a battering ram. Two officers approached one of the windows of Lemp’s bedroom.

According to what prosecutors said the SWAT team members told them, one of the two officers at the window used a “break and rake” tool to smash out the top pane and pull away the shade. The second officer moved his rifle and flashlight inside the window, yelling for Lemp and his girlfriend to put their hands up. His job: provide cover as his teammates rammed through the front door — which they did, with several of them making a quick left toward Lemp’s bedroom, set off by a set of glass French doors covered by blinds.

The shooting officer told prosecutors he had a line of sight on Lemp and his girlfriend lying across their bed. He yelled at them to put their hands up, which the girlfriend did as she got out of bed, according to the officer’s recollections in the report. Lemp never put his hands up, the officer said.

Prosecutors said the officer who fired saw that Lemp had bent down and picked up a rifle. The officer “believed he started saying, ‘don’t do it. Don’t do it’ to Lemp but couldn’t be entirely sure.” Lemp continued to raise the rifle “to a point where the muzzle was directly pointed at the officer himself.” The officer thought Lemp was going to kill him, “so he made the decision to shoot Lemp.”

The officer fired. That is about when the interior team arrived outside the bedroom, according to the report. Without knowing who had shot whom, one of these SWAT officers wedged the door open enough to toss a high-decibel “flashbang” grenade into the bedroom.

In testimony before a grand jury, Lemp’s girlfriend said she was awaked by “an explosion that she thought was gunshots,” prosecutors wrote. She testified that after hearing gunshots, she “dove for cover at the same time as Duncan was kind of starting to stand, sit up, and then stand up right beside the bed,” according to the report. And she said Lemp began firing shots at the officer, the report said.

But according to prosecutors, evidence from the scene contradicted two of these assertions. First, if she awoke to gunshots, the officer would have had to have fired before the glass broke, shooting through a closed shade, but there were no bullet holes in the shade. Secondly, according to the report, Lemp’s gun was shown not to have been fired that morning.

Her recollection that Lemp raised his gun, however, confirmed a key part of the officer’s account — that Lemp had pointed a gun toward the window, according to the prosecutors’ findings.

The report included about two pages worth of text messages between Lemp and his mother, which prosecutors say helped explain his state of mind and preparation for a possible raid.

“Do you know what a no-knock warrant is?” Lemp wrote to his mother on Nov. 19, 2019. “A red flag law? We’re one angry phone call away from a swat teams only warning being the first battering ram hit.”

A month later, Lemp’s mother texted him her concerns.

“You are going overboard with this stuff love and I’m honestly worried about you and us,” she wrote on Dec. 11. “You’re behaving in a manic way. One or 2 things might be understandable but you keep buying more and more things you will never use. If you were to ever use, would be the destruction of you and everyone around you.