The parents of Ramarley Graham, an unarmed teenager killed by the police in the Bronx, tried to give Mayor Bill de Blasio and his wife a letter at City Hall on Tuesday, the fourth anniversary of their son's death.

Joined by the families of others killed by the police, the couple said they would then spend the night in front of the office of U.S. Attorney Preet Bharara, who is investigating Graham’s death.

“Today marks four years since they murdered my son,” said Franclot Graham, the father, during the rally. “You’re the mayor. I’m demanding you fire these officers. We need justice.”

Ramarley Graham, 18, was killed in the Bronx in 2012 by a police officer who said he thought Graham was armed. Graham was spotted by the police near a bodega, and the officers followed him to his apartment and kicked down the door before the shooting. Police said he was trying to flush pot down the toilet before he was killed. His grandmother and 6-year-old brother were home.

A Bronx grand jury voted to indict the officer who killed him, Richard Haste, in 2012, but a state judge dismissed the decision in 2013. The judge said that prosecutors gave the wrong instructions to the grand jury. A second grand jury then decided not to indict Haste in August of that year.

The Department of Justice’s Southern District has since been investigating Graham’s death since 2014.

The teen’s father and mother, Constance Malcolm, tried to give the letter to de Blasio and Chirlane McCray after the rally. The mayor wasn’t there, but the letter was given to his staffers.

“Ramarley was unarmed, not committing a crime, and was home where he should have been safe,” said the letter. “For the past four years, we have been fighting for justice for our son and other black and brown people in our city and country who face the injustices of abusive policing and brutality.”

City Hall spokeswoman Monica Klein called Graham’s death “a tragedy” and noted in a statement that “Under Mayor de Blasio, the NYPD has piloted body cameras, retrained its officers and established new Use of Force guidelines — all part of the Mayor’s pledge to strengthen the relationship between police and the communities they serve.”

Graham’s parents asked for the mayor and Police Commissioner Bill Bratton to fire the officers involved in the shooting, and said that Haste was given a pay raise since Graham’s death.

“He is on modified duty and has been served departmental charges,” said the NYPD in a statement on Haste. “The internal case is on hold pending the Department of Justice investigation.”