After federal prosecutors declined to file civil rights charges against two U.S. Park Police officers who shot and killed unarmed motorist Bijan Ghaisar in 2017, Ghaisar’s family and lawyers turned their focus Friday to prosecutors in Virginia with the hopes that a state criminal case could be built against the officers.

Charging a federal officer under state law is difficult but could be done, Fairfax County Commonwealth’s Attorney Raymond F. Morrogh said Friday. He said he has told the Ghaisar family he would examine the evidence and consider a case, but his term is ending soon and it is not clear how his successor will proceed.

Also Friday, a letter written by the Justice Department to the Ghaisars revealed that the two officers fired a total of 10 shots at him, not nine as previously reported, and the officer who was driving during the pursuit fired all four of the fatal shots.

The news that Officers Alejandro Amaya and Lucas Vinyard would not face federal civil rights charges in the 2017 slaying was delivered by letter to the Ghaisars’ lawyer Thursday afternoon, rather than in a face-to-face meeting as the Justice Department had promised, and was then announced in a news release before the family was informed. At a news conference Friday morning in Washington on an unrelated matter, U.S. Attorney Jessie K. Liu refused to answer questions about her office’s decision not to charge the officers, why the decision took two years or why her office declined to meet with the Ghaisars before announcing the decision.

Though the Justice Department ruled out federal charges against the officers, the letter to the Ghaisars said its decision on whether a civil rights crime was committed “does not preclude other components of the U.S. Department of Justice, other agencies, or state authorities from taking action, where appropriate, under their separate enforcement authority.” The letter was signed by James Felte, chief of the criminal section of the Justice Department’s Civil Rights Division, and T. Patrick Martin, criminal division chief for the U.S. attorney’s office in Washington.

The letter does not explain why the officers fired their weapons, or say whether the officers were interviewed. As suspects in a criminal case, Vinyard and Amaya were not required to give statements to the FBI, which investigated the case, as part of their Fifth Amendment right not to incriminate oneself. They are also defendants in a civil suit filed by the Ghaisars, where they may be compelled to give depositions or trial testimony. A spokeswoman for Liu said no written report would be issued about the Ghaisar case, as was done in high-profile cases such as those of Michael Brown in Ferguson, Mo., and Alton Sterling in Baton Rouge.

The decision not to file federal charges raises the question of whether prosecutors in Fairfax County, Va., where the shooting occurred, could charge Amaya and Vinyard. “We have always said and continue to feel,” said Roy L. Austin, the Ghaisars’ lawyer, “that the Commonwealth of Virginia should have been playing a larger role in this investigation. A Virginia citizen was shot and killed by federal officers improperly acting on Virginia property, recklessly putting Fairfax officers in potential danger.”

Morrogh said he met with the Ghaisars not long after the Nov. 17, 2017, shooting, and “I promised the family that I would review the case” after federal authorities were done. “I didn’t promise them I would prosecute it. It’d be a tricky case. But if I looked at it and thought this was not a reasonable shooting, I’d prosecute it.”

However, Morrogh, a 35-year veteran of the Fairfax prosecutor’s office, was not reelected recently and his term will end in January. His successor, Steve Descano, a former federal tax prosecutor, declined to answer any questions about whether he would review the case or consider prosecuting the officers when he assumes the commonwealth’s attorney’s job.

The episode actually began in Alexandria, Va., where Ghaisar stopped his Jeep Grand Cherokee in a southbound lane of traffic on the George Washington Memorial Parkway. The Jeep was struck from behind by a Toyota Corolla, and Ghaisar then drove off, the Corolla driver reported. It is not known whether Ghaisar knew his Jeep had been hit by the much smaller Corolla, and photos of Ghaisar’s Jeep do not indicate any significant damage. The Corolla driver was working for Uber, and he said his passenger called 911 to report the fender bender. Authorities have declined to release that call.

The Justice Department’s letter to the Ghaisars identifies Vinyard, 38, as the driver of the Park Police vehicle and Amaya, 40, as the passenger. The two officers spotted Ghaisar’s Jeep in the Fairfax County section of the parkway and signaled for it to pull over, while a Fairfax County police lieutenant pulled in behind the Park Police and recorded the incident on his in-car camera.

When Ghaisar first stopped, Amaya is seen on the Fairfax video running to Ghaisar’s window with his gun drawn, watching Ghaisar drive away, and slamming his gun into the side of Ghaisar’s Jeep, apparently ejecting the gun’s magazine. He picked up the magazine and got back in his vehicle, the video shows.

Ghaisar pulled over a second time on an exit from the parkway, and both Amaya and Vinyard ran toward his Jeep with guns drawn. Ghaisar again drove away, and Amaya is seen kicking the Jeep on the video.

At a third stop in the Fort Hunt neighborhood of Fairfax County, Vinyard pulled his vehicle in front of Ghaisar’s Jeep, the video shows. Amaya emerged first and, with Vinyard soon behind him, both aimed their weapons at Ghaisar. Ghaisar again started to slowly pull away, and both officers opened fire.

The Justice Department letter to the Ghaisars states that the FBI did “extensive ballistics and trajectory analyses” and determined that each officer fired five shots. Amaya only hit Ghaisar in the wrist, but Vinyard hit Ghaisar four times in the head, according to the letter. A video of the shooting, released by Fairfax police, seems to indicate only nine shots were fired, but two of the shots may have been fired simultaneously.

“To support a civil rights prosecution,” Felte and Martin wrote to the Ghaisars, “we must prove beyond a reasonable doubt not only that Amaya and Vinyard knowingly and intentionally fired upon your son, but that they did so with the specific intent to deprive him of the right to be free from an unreasonable use of force. This is a higher standard of proof than is commonly required under state law.” The lawyers added that they would have to prove beyond a reasonable doubt that “a reasonable officer in the same situation as Amaya and Vinyard would not have perceived any threat of serious bodily harm to themselves or others.”

The Justice Department concluded that they could not prove “beyond a reasonable doubt that the officers did not perceive a deadly threat, even if that perception was mistaken or the result of poor judgment.” The decision relies in part on the seminal Supreme Court ruling of Graham v. Connor, which ruled that “The ‘reasonableness’ of a particular use of force must be judged from the perspective of a reasonable officer on the scene, rather than with the 20/20 vision of hindsight."

“It is very difficult to hold a police officer responsible for civil rights violations,” said Christy E. Lopez, a former deputy chief in the Civil Rights Division who now teaches at Georgetown Law Center. She said in addition to reasonableness, the officers must also have acted willfully. “You can have unreasonable use of force,” Lopez said, “but as long as you didn’t willfully behave unreasonably, you can’t be criminally prosecuted.” She said the Supreme Court had ruled that a fleeing vehicle could be considered a threat, which may have factored into the Justice Department’s ruling.

If the case were to be prosecuted under state law, the “willfulness” component would be eliminated, Lopez said. “There’s been absolutely no accountability in this case,” Lopez said of the Ghaisar shooting. “When that happens, the culpability is on all of us. If we fail to hold officers accountable, then we’re all culpable.”

Morrogh noted that he successfully prosecuted a Fairfax County officer in state court in 2015 for the fatal shooting of John B. Geer, with Officer Adam D. Torres pleading guilty to involuntary manslaughter. But that case did not involve federal officers.

The federal supremacy clause, which holds that federal authority trumps state authority, can prevent prosecution of federal officers in many cases.

Morrogh and others said a recent case from Texas defined the standard for prosecuting a federal officer in state court. In 2013, an Austin officer working on an FBI task force encountered a man after a bank robbery in Austin, got into a scuffle with the man, then shot and killed him. The state prosecutor in Austin indicted the officer for manslaughter, the case was moved to federal court and a judge there dismissed the case in 2015. The Austin prosecutor appealed to the U.S. Court of Appeals for the 5th Circuit and lost, then appealed to the Supreme Court, which declined to hear it last year.

“The Supremacy Clause” of constitutional law “prohibits a state from punishing” a federal officer, wrote 5th Circuit Judge Stephen A. Higginson, who was authorized by federal law to perform an act, who “did no more than what the officer subjectively believed was necessary and proper, and that belief was objectively reasonable under the circumstances.”

Morrogh said if a state prosecutor attempted to charge a federal officer, the case would first be moved to federal court. Then, in a pretrial hearing, “I’d have to affirmatively disprove self-defense in a hearing, as opposed to the officers have to prove self-defense. I’m not saying it’s impossible, but I’d have to see the evidence,” Morrogh said. If a federal judge were to allow the state prosecution to move forward, it would proceed under state law.

In a Yale Law Review article in 2003, former solicitor general Seth P. Waxman and Cornell law professor Trevor W. Morrison wrote that “federal officers acting within the scope of their employment should be immune from state prosecution for taking any action that they reasonably believe is necessary and proper to the performance of their federal functions.” As in the 5th Circuit case and the Graham v. Connor Supreme Court case, Waxman and Morrison repeatedly emphasized the term “reasonable.” Waxman declined a recent request to discuss the article, which was written after he had successfully defended FBI Special Agent Lon Horiuchi from state prosecution in the killing of Randy Weaver in an incident at Ruby Ridge, Idaho, in 1992.

Bryanna Fox, an associate professor of criminal justice at the University of South Florida and a former FBI agent, said the Graham v. Connor standard of not analyzing an officer’s actions in hindsight made charging an officer difficult. A fleeing felon can be considered a threat, Fox said, or the Park Police officers may have thought that Ghaisar was reaching for a gun. “We don’t know anything from the officers’ point of view,” Fox said. “They don’t have to be right, they just have to be reasonable.” She said her FBI training taught her that “just because you legally can do it doesn’t mean you should do it.”