(Claritza Jimenez/The Washington Post)

The white pickup truck roared up the street in Adams Morgan, sending a traffic sign into the air. Then came screeches and screams. A bicycle upended, its wheels spinning. A police officer face down and motionless on the pavement.

The Dodge Ram then slammed into a recycling truck, crumpling its front end. Two policemen and a Transportation Department officer had been struck by the pickup, police said, with one young officer suffering life-threatening injuries.

Bob Rogan, chief of staff to Rep. Peter Welch (D-Vt.), ran from a coffeehouse and reached the truck’s dazed passenger as he climbed from the wreckage, a cut on his forehead. Rogan said the man told him that he and his friend had been to a club and smoked something.

“ ‘I told him not to do this,’ ” Rogan recalled the passenger saying. “ ‘I told him to slow down, and he wouldn’t slow down.’ ” Rogan said the driver remained behind the wheel, swaying slightly and appearing disoriented.

D.C. police arrested the two men in the pickup, both from a rural county in Virginia 40 miles south of Richmond, as investigators tried to piece together what caused Thursday night’s crash along the 2400 block of 18th Street NW, in the heart of one of the District’s most vibrant and busiest nightlife areas. A police report says that in the pickup’s back seat, investigators found a military-style weapon described as a Romarm Cugir rifle, the Romanian version of the AK-47. It was not clear why the men had the gun.

The scene in Adams Morgan on Thursday after two officers were struck. (Clarence Williams/The Washington Post)

Police identified the driver as Brandon Figures-Mormon, 22, of Disputanta, Va., who was charged with assault with intent to kill and illegal possession of a firearm. They said the passenger was Dwayne Nicholas Taylor, 23, of Prince George, Va.

Taylor was charged with possession of an unregistered firearm, but the District’s Office of the Attorney General dropped it before Taylor’s initial appearance Friday in D.C. Superior Court. A spokesman said only that the decision was “based on our review of the evidence.” Charges against Figures-Mormon remain.

D.C. police Chief Peter Newsham called the decision involving Taylor disappointing, adding that a “case involving three District employees deserves more consideration.” The chief said there is no evidence that the crash was the result of terrorism, but he said that authorities have not ruled out the possibility that the driver intentionally targeted police officers.

A man who answered the phone at Taylor’s house identified himself as a relative but declined to talk. Relatives of Figures-Mormon could not be reached. He did not have a court appearance Friday.

Authorities said they are awaiting results of toxicology tests to determine whether either man was impaired. Court records show that in 2014, Figures-Mormon pleaded guilty to assault in Virginia — a charge that had been reduced from assaulting a police officer — and received a year-long suspended sentence. His social media accounts indicate an affinity with mysticism. He enlisted in the U.S. Marine Corps in 2012 but was discharged a year later because the “character of his service was incongruent with Marine Corps’ expectations and standards.” A military spokesman declined to elaborate.

Meanwhile, police and residents were keeping a close eye on the injured. The Transportation Department officer was identified in a police report as Pamela Ann Johnson, 56, an eight-year veteran of the agency.

The report identifies one of the injured officers as Richard R. Duranne, who has been on the force for four years. He is married and has two children, ages 2 and 4. Duranne was in fair condition at a hospital Friday.

The most severely injured officer, Alen Bukvic, who is married, was at MedStar Washington Hospital Center Friday in critical but stable condition. “His prognosis is unclear at this time,” Newsham warned Friday afternoon. But later, after Newsham visited Bukvic, he said that although the officer could not speak, “he was able to communicate by way of writing, which I took as a very good sign.”

The officers are part of the police department’s nightlife detail, which works exclusively in areas densely populated with bars, nightclubs and restaurants.

Newsham said the incident began a few minutes before 9 p.m. on 18th Street Northwest, just after Belmont Road. He said a northbound Metrobus stopped behind a car and began letting off passengers. Newsham said the pickup truck was several cars behind the bus.

Noticing a backup, the two bicycle officers and the Transportation Department control officer made their way to the bus. They stood in a wide median strip marked in yellow, a spot where officers frequently stand. One officer got off his bicycle and began directing traffic while the other officer remained on his bicycle.

Newsham said the pickup’s driver veered out of the line and raced up the medium strip, striking the three workers. The truck, he said, “didn’t appear to slow down.” The pickup then crashed into a the recycling truck.

Newsham praised bystanders, the paramedic, fire crews and emergency room doctors. He made special mention of the Metrobus driver, who he said was seen on video running to the most severely injured victim to help before paramedics arrived.

“He was instrumental in saving our officer,” he chief said.

Keith L. Alexander, Magda Jean-Louis and Paul Schwartzman contributed to this report.