For the first time in nearly two decades, a former Philadelphia police officer was charged Tuesday in an on-duty shooting, and the city's reform-minded top prosecutor characterized the case as an example of police accountability that was long overdue.

District Attorney Larry Krasner said that after a yearlong investigation, a grand jury had determined that Ryan Pownall — formerly an officer in the 15th District — should face counts of murder and related offenses for unnecessarily firing his weapon at 30-year-old David Jones when Jones ran from a traffic stop in June 2017. Jones later died from two gunshot wounds to the back.

Pownall was arraigned Tuesday afternoon on charges of murder, possession of an instrument of crime, and reckless endangerment, and was denied bail, according to court records. His preliminary hearing is scheduled for Sept. 19.

At a news conference, Krasner described the charges against Pownall as "applying justice even-handedly," and added that it was "regrettably unusual" that officers in Philadelphia have infrequently faced criminal consequences for questionable or problematic conduct.

"This is a city, like many other American cities, where there has not been accountability for activity by police officers in uniform, especially when that activity involves violence against civilians," said Krasner, who spent three decades as a defense attorney and specialized in police misconduct cases before being elected district attorney.

Hours after Krasner's announcement, a police union official called the case against Pownall an "absurd disgrace," saying the union would seek to have the charges downgraded and get Pownall released on bail.

"Today's meritless indictment clearly illustrates a district attorney who has an anti-law-enforcement agenda," John McNesby, president of Fraternal Order of Police Lodge 5, told reporters and about 100 supporters at the union's Northeast Philadelphia headquarters. Joining him on stage were Pownall's wife, Tina, and brother, Edward.

The case illustrates how the relationship between the city's police force and top prosecutor has been marked by bouts of tension and disagreement. It also provides the first example of Krasner's acting on a campaign promise — which he reiterated after being sworn in — that he would pursue cases against police officers if the evidence supported it.

The decision to charge Pownall was a measure of relief for Jones' father. "It doesn't bring him back," Thomas Jones, 48, said, "but hopefully [we] continue to get justice."

It also drew immediate praise from activists who last year staged near-daily protests and disruptions after the shooting, as well as other Krasner supporters.

Isaac Gardner and Christopher Norris, two of the most visible protesters, hailed the decision outside the District Attorney's Office as soon as Krasner's news conference ended, with Gardner saying Krasner was "stepping up and doing the right thing." Asa Khalif – who had been arrested while demonstrating for Pownall's arresttweeted: "Good job Larry Krasner!"

Pownall, 36, was dismissed from the Police Department last year over the shooting, with Commissioner Richard Ross citing a host of departmental violations and saying Pownall displayed "poor judgment" during the altercation with Jones.

According to a grand jury report detailing Pownall's arrest, Pownall had been transporting a father and two children to the Special Victims Unit for an interview on June 8, 2017, when he spotted Jones riding a dirt bike near Whitaker and Hunting Park Avenues.

"Look at this motherf–r," Pownall is quoted as saying. He then drove across traffic and sought to stop Jones while the three witnesses remained in the back seat of his police SUV, the report says.

The report says Pownall cursed at Jones, and then frisked him and felt a gun. A struggle ensued, but Jones broke free and ran away, according to the report. Pownall tried to fire his service gun but it jammed. He fixed it and fired at least three shots, the report says, striking Jones twice in the back.

Jones' weapon — which he was barred from legally owning because of his previous felony convictions — was later found on the ground "roughly 25 feet from where Pownall was firing, in the opposite direction of Jones' flight," the report says.

"[Jones'] death was not necessary to secure his apprehension – an apprehension that would never have been necessary if Pownall had not incited the confrontation," the report says.

Fortunato Perri Jr., Pownall's lawyer, said Tuesday that Pownall was "legally completely justified in his actions, and he will be exonerated of all charges. "

The last on-duty officer charged for a shooting in Philadelphia — Christopher DiPasquale in 1999 — did not go to trial because two judges dismissed the charges against him.

Pownall, who is white, was involved in 2010 in another on-duty shooting of a black man from behind.

In that case, Pownall was one of several officers who fired at Carnell Williams-Carney, who had run away from police in Frankford. Pownall later testified that he believed he fired the shot that struck and paralyzed Williams-Carney, although ballistics tests could not be conducted because the bullet remains lodged in his back.

Last month, Philadelphia Weekly and City & State PA published a joint investigation reporting that Pownall had been the subject of 15 civilian complaints between January 2013 and March 2018, the third-highest total of any officer on the force.

Earlier this year, the out-of-work Pownall was hired by the Philadelphia Parking Authority as a maintenance employee. He quickly resigned after colleagues raised concerns about it.