The two U.S. Park Police officers who fatally shot unarmed motorist Bijan Ghaisar in 2017 will not be charged with any crimes in connection with the incident, federal prosecutors said Thursday. The decision came just days before the second anniversary of the slaying.

Ghaisar’s family and a number of elected officials expressed outrage both at the decision and the lack of any explanation for the shooting.

Officers Alejandro Amaya and Lucas Vinyard pursued Ghaisar down George Washington Memorial Parkway shortly after 7:30 p.m. Nov. 17, 2017, after he left a fender bender in Alexandria.

Ghaisar, 25, briefly stopped twice and then drove away each time as the officers ran toward him with guns drawn, video released by Fairfax County police shows. After a third stop, Ghaisar again pulled away as Vinyard and Amaya aimed their guns at him, the video shows, and the officers fired nine times into Ghaisar’s Jeep.

In a statement issued by U.S. Attorney for the District Jessie K. Liu, officials said they could not prove the officers committed a “willful violation” of civil rights law. But her statement did not explain why the men shot into a vehicle as it drove away from them.

The Ghaisar family has sued the officers in federal court in Alexandria. In that case, the officers say they fired in self-defense.

Ghaisar’s family, with the support of Sens. Charles E. Grassley (R-Iowa), Mark R. Warner (D-Va.) and others, had pressed for details of the investigation in the months and years following the killing. Family and friends demonstrated outside the Justice Department repeatedly and outside the Interior Department. They are planning a vigil at the Lincoln Memorial on Sunday to mark the second anniversary of Ghaisar’s death.

The shooting also prompted legislation that would require federal officers to wear body cameras.

The family was notified of the decision in a letter hand-delivered to their lawyer, Roy Austin, shortly after 3:15 p.m. Thursday, Austin said. The Ghaisars had been told by Justice officials that they would be informed in person before a decision was announced.

“Today’s decision was a cowardly act by a Department of Justice that is afraid to hold law enforcement, especially federal law enforcement, accountable when it commits murder,” the Ghaisars said in a statement. “Let’s be clear about what happened here: Two people executed an American citizen who they were sworn to protect and serve, and the only reason they’re escaping justice is because they wear badges.”

The Ghaisars said the decision not to charge was “another betrayal in this nightmare that began for us almost two years ago to the day . . . they have broken every promise made to us — from keeping us informed about the investigation to personally sharing the results before broadcasting it to the world to, most importantly, protecting Bijan.”

Amaya and Vinyard did not return phone calls seeking comment Thursday.

“This is not justice,” said Rep. Don Beyer (D-Va.), who had helped the family push for answers and sponsored legislation requiring federal police to use cameras. “The Justice Department failed our community for two years by withholding answers about why police killed Bijan Ghaisar, but this final failure is the worst of all.” He said “all available evidence, including video of the event, contradicts” Liu’s conclusion that no crime occurred.

Grassley and Warner issued a joint statement that said the decision not to charge the officers “will only add to this family’s heartbreak. The Department’s statement also adds to the long list of questions that remain unanswered years later, despite a two-year investigation. The Ghaisars deserve to understand what happened to Bijan.”

The two senators said they would request a formal briefing from the Justice Department within the next 30 days “to understand what went into the decision not to pursue charges in this case.”

The Ghaisars were hopeful that, if federal authorities declined charges, the Fairfax County prosecutor would take up the case. Newly elected Commonwealth’s Attorney Steve Descano declined to comment Thursday on whether he would investigate the shooting.

Ghaisar was an accountant with no criminal history, born and raised in Northern Virginia. He graduated from Langley High School and Virginia Commonwealth University, lived by himself in an apartment in Tysons and worked for his father’s accounting firm in McLean. He was single with no children.

On Nov. 17, 2017, Ghaisar was driving his Jeep Grand Cherokee south on George Washington Memorial Parkway when he stopped in a lane of traffic north of Alexandria and was rear-ended by a Toyota Corolla, operated by an Uber driver with a passenger. Ghaisar drove off, and the passenger called 911, the driver said. Authorities have refused to release the 911 recording, and the passenger has declined to comment.

In the Fairfax County section of the parkway, Amaya and Vinyard spotted the Jeep and pulled behind it with lights and siren on. A Fairfax police lieutenant also joined the pursuit, recording with his in-car camera.

Ghaisar stopped once, was approached by the armed officers, and drove off. Several miles later, Ghaisar pulled off the parkway and stopped again. Again, the officers ran at him with guns drawn, and he drove off. At an intersection in the Fort Hunt neighborhood, Ghaisar stopped again. The officers pulled in front of the Jeep, and as Ghaisar slowly maneuvered away again, both Vinyard and Amaya opened fire, the Fairfax police video shows.

Ghaisar’s family said he was shot four times in the head. The Park Police waited five hours before notifying Ghaisar’s parents that he’d been shot, and they did not tell them who was involved, the Ghaisars said. No weapon was found in Ghaisar’s Jeep.

Ghaisar lived for 10 days before he was removed from life support on Nov. 27, 2017, in the same hospital where he was born.

Fairfax County Police ChiefEdwin C. Roessler Jr. later released the videos from his officers. The FBI took over the case, and the U.S. attorney’s office in Alexandria recused itself from handling the prosecution.

In the statement, Liu said that the FBI had interviewed more than 150 people in its investigation. Liu said the government had to prove that the officers acted “willfully” to deprive Ghaisar of a constitutional right, in this case his Fourth Amendment right to not be unreasonably seized.

Liu said the Supreme Court has interpreted that “to mean they acted with a bad purpose to disregard the law. As this requirement has been interpreted by the courts, evidence that an officer acted out of fear, mistake, panic, misperception, negligence or even poor judgment” cannot establish a federal civil rights violation.

The statement did not comment on the officers’ state of mind at the time of the shooting, and there was no indication whether Vinyard or Amaya were interviewed by the FBI. As suspects in a potential criminal case, they were not required to speak to criminal investigators, though they are required to speak to Park Police internal investigators.

Neither Liu nor the Justice Department issued a written report about the case, as was done in other high-profile civil rights cases such as Michael Brown in Ferguson, Mo., and Alton Sterling in Louisiana.

Park Police policy states that “an officer may use deadly force only when necessary,” and only when he or she has a “reasonable belief” that the subject “poses an imminent danger of death or serious bodily harm to the officer or to another person.” The use of deadly force on “fleeing felons” is only justified, the department policy states, if “the individual has committed a felony involving the infliction or threatened infliction of serious physical injury or death and the escape of the individual would pose an imminent threat of serious physical harm.”

Similarly, Park Police policy discourages the firing of guns at moving vehicles. “Officers shall not fire at a moving vehicle,” the policy states, “except when the officer has a reasonable belief that the subject poses an imminent danger of death or serious physical injury to the officer or to another person.”

Little is known publicly about Vinyard and Amaya, who are both married with children. Amaya, 40, has been a Park Police officer since September 2009. Vinyard, 38, has been a Park Police officer since September 2007.

Both officers were initially placed on leave with pay, then placed on administrative duty with pay, the Park Police said.

The lawsuit against the officers and the Park Police is still pending in federal court in Alexandria. An internal investigation of Amaya and Vinyard, which was stayed pending the determination on charges, can now move forward.

The Park Police issued a statement saying that “the loss of Bijan Ghaisar has impacted many people, including his family, friends, and our community” and that it was reviewing the FBI’s findings.

“We are not giving up on justice for Bijan,” the Ghaisars said in their statement. “At the very least, these rogue officers should be fired. Other criminal charges and prosecution are also possible through the Commonwealth of Virginia. We demand justice — and we will continue to fight for it until we get it.”