Sens. Charles E. Grassley (R-Iowa) and Mark R. Warner (D-Va.) continued their campaign Wednesday for answers in the 2017 killing of Bijan Ghaisar by two U.S. Park Police officers, who the Justice Department decided last week would not face federal charges.

The two senators requested a briefing from FBI Director Christopher A. Wray about the case. They’ve also sought answers in a series of letters they have sent to the FBI beginning last year, which the agency has previously declined to provide.

In addition, three members of Congress have asked the FBI to allow the release of the 911 call made at the beginning of the incident. The call may shed light on why the officers repeatedly approached Ghaisar’s Jeep Grand Cherokee with guns drawn after Ghaisar left the scene of a minor fender bender in Alexandria on Nov. 17, 2017, then fired at him 10 times as he drove away from them. Ghaisar was struck four times in the head and died 10 days later.

“Investigations into the use of deadly force must be handled in a way that reinforces public confidence in law enforcement,” Grassley and Warner wrote to Wray. “Despite nearly two years of investigating this incident in which considerable FBI resources were used, the Ghaisar family, Congress, and the general public still do not have all the answers. The FBI needs to provide a full and thorough account of the events that led to Mr. Ghaisar’s untimely death.”

“We are enormously grateful to Sens. Grassley and Warner,” said Kelly Ghaisar, Bijan Ghaisar’s mother, “for their relentless efforts to get the answers that have been denied to us for so long. Their commitment to transparency and justice for Bijan has given us hope and comforted us in the darkest of times.”

Ghaisar, 25, was an accountant and Northern Virginia native who was driving south on the George Washington Memorial Parkway when he stopped in a lane of traffic about 7:27 p.m. on Nov. 17, 2017. His Jeep was struck from behind by a Toyota Corolla being driven for Uber, with a passenger in the back, a Park Police report shows. The driver told The Washington Post that the Jeep’s driver then drove off without speaking to him and that the passenger dialed 911. The call was routed to the Arlington emergency communications center, which has declined to release the tape on advice of the Justice Department. The passenger has declined to comment.

In a letter sent Monday to the FBI, Reps. Don Beyer (D-Va.) and Jennifer Wexton (D-Va.) and Del. Eleanor Holmes Norton (D-D.C.) wrote: “Given that the Department of Justice review of the case is concluded, there should be no impediment to its disclosure now. As you know, we found the two-year period it took to resolve the case unacceptable and remain concerned with the result. … The people of the National Capital Region demand high transparency and accountability standards from their local government and law enforcement entities. We ask that you allow the local entities to publicly release the 9-1-1 records affiliated with the Ghaisar case.”

Beyer, Norton and Wexton all spoke at a protest gathering Sunday at the Lincoln Memorial to mark the two-year anniversary of Ghaisar’s shooting, and all said more information was needed.

After Ghaisar left the scene of the fender bender, he was spotted minutes later by Park Police Officers Lucas Vinyard and Alejandro Amaya, who followed the Jeep and signaled for it to pull over. Twice Ghaisar stopped, then drove off as Amaya and Vinyard ran toward him with guns drawn. A Fairfax County police lieutenant who followed the pursuit recorded the episode on his in-car camera. Federal police do not have body cameras or in-car cameras, and Beyer and Norton have introduced legislation to require such cameras for uniformed federal officers.

At an intersection in Fairfax County, Ghaisar stopped a third time. As the officers got out again, Ghaisar again started to roll away from them. The video shows both officers opening fire, and the Justice Department said each officer fired five times. Ghaisar was unarmed, and no drugs or alcohol were found in his Jeep.

Warner and Grassley have written letters to the FBI, the Justice Department and the Interior Department seeking answers beginning in January 2018, but the agencies largely demurred because the investigation was ongoing. Last week, the Civil Rights Division of the Justice Department and the U.S. attorney in Washington, Jessie K. Liu, announced that Amaya and Vinyard would not face federal criminal civil rights charges. In a letter delivered to the Ghaisars’ lawyer, the government did not preclude other agencies from pursuing the case but said it 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.”

Liu declined to answer questions about the case at a news conference the next day. The two-page letter to the Ghaisars explaining the decision not to file charges said the FBI had interviewed “over 150 individuals” and that extensive ballistics and trajectory analyses were performed after the shooting. But it did not say whether Amaya or Vinyard were interviewed, what their explanations were for the shooting, or whether there were other witnesses to the shooting besides those two officers and the two Fairfax officers who followed the pursuit and were present when the shots were fired. Amaya and Vinyard have been sued by the Ghaisars in federal court in Virginia, and their attorneys argued that they acted in self-defense. The two officers have not spoken publicly about the case.

Grassley and Warner asked the FBI to respond to their previous letters and to provide them a briefing on the case no later than Dec. 15.

According to the author of a 2016 report on police shootings in Washington, the federal prosecutor in Washington has never charged a D.C. officer with a crime for an on-duty shooting. It could not be determined whether any federal officer had ever been charged. Four Park Police officers who were involved in the fatal 2009 shooting of Trey Joyner were not charged.