Montgomery County crash investigators could never determine the exact speed Fernando J. Valenzuela was driving the night he rammed a Honda Civic into two men walking along a street, killing one of them. But evidence from the scene offered chilling clues.

The hood was crumpled. The windshield was demolished. The belongings of the two victims — Billie Jay Genies and brother James Robert Genies — were scattered after impact.

“It knocked both of the brothers out of their shoes,” prosecutor Eric Nee said in Circuit Court on Tuesday, moments before a judge accepted Valenzuela’s guilty plea on charges of second-degree murder and first-degree assault.

Valenzuela, 21, of Damascus faces up to 20 years in prison. He is scheduled to be sentenced Aug. 1.

The events that unfolded the night of Dec. 4 involved the consumption of beer, a chance meeting at a 7-Eleven in Damascus, a ride to Gaithersburg and a parting of ways, according to arrest records and Nee’s account aired in court Tuesday. Valenzuela grew angry when the brothers left his car without paying him for the ride, Nee said; he drove after them and ran them down.

Fernando J. Valenzuela (Courtesy of Montgomery County Police Department)

James Robert Genies was knocked out but survived. Billie Jay Genies suffered massive head injuries and died at the scene. Valenzuela pleaded guilty to “depraved heart murder,” which is the killing of another person “while acting with an extreme disregard for human life,” according to instructions typically given to jurors in such cases.

Valenzuela’s attorney, Andrew Jezic, said he will argue at sentencing that his client never meant to kill anyone and is extremely sorry for what happened. “Sitting in solitary confinement for several months, Fernando prayed and reflected a lot, and decided to take responsibility for his actions,” Jezic said.

Valenzuela’s mother, father, a former boss and others have sent letters to the court offering another side of his character. He graduated from a military high school in Florida and has worked for his father’s construction business and a Chipotle Mexican Grill restaurant. “I know for a fact that he is truly remorseful for the loss of life and the hurt and pain he has caused,” wrote a local pastor, Luis Rafael Rodriguez.

Family members of the Genies brothers attended the plea hearing Tuesday, but they declined to comment afterward.

In court, Nee revealed the case he would have put forward had the case gone to trial. On Dec. 4, Valenzuela and a friend bought a 12-pack of Blue Moon beer and were joined by a third friend in Damascus, Nee said. One witness would later tell authorities that Valenzuela drank five or six of the beers. Two witnesses described him as drunk.

Just after midnight, Nee said, the three drove to a nearby McDonald’s, found it closed and went to a 7-Eleven across the street. There they encountered the Genies brothers, whom they had never met before.

Valenzuela offered the brothers a ride to Gaithersburg, where they promised an opportunity to buy marijuana, Nee said. On the way there, the group seemed to be getting along. “The Genies brothers had some CDs. They were rapping. There was no animosity amongst the individuals,” Nee said.

After arriving in Gaithersburg, Valenzuela “got out of the car to relieve himself,” Nee said, adding that the Genies brothers followed suit. But they did not return to the car and kept walking. Valenzuela became upset that he received neither money for the ride nor marijuana, Nee said.

Valenzuela began slowly following the Genies brothers — driving about 10 mph — as they walked into a neighborhood. Words were exchanged. At some point, Valenzuela drove past the two men, circled back around and followed them again. His friends would later indicate to investigators that he made incriminating remarks. “I’m going to hit them . . . I’m going to run them over,” Valenzuela said, according to Nee. His friends did not believe him.

But Valenzuela accelerated, swerved to the right and struck both men. James Robert Genies was released from the hospital around noon on Dec. 5, Nee said.

Together, the two counts — second-degree murder and first-degree assault — carry a maximum sentence of 55 years. State sentencing guidelines call for between 12 to 28 years, Jezic said. The maximum incarceration, under the plea deal, is in the middle of those guidelines, he added.