​​ROCHESTER, N.Y. — ​The man accused of fatally shooting Rochester Police Officer Anthony Mazurkiewicz late last month is facing eight counts of aggravated murder, murder in the second degree, aggravated attempted murder, attempted murder in the second, two counts of assault and two counts of criminal possession of a weapon, Monroe County District Attorney Sandra Doorley announced Wednesday. 

Investigators say 21-year-old Kelvin Vickers snuck up on a van occupied by Officer Tony Mazurkiewicz and his partner Sino Seng as they were parked on Bauman Street on July 21 and opened fire. Mazurkiewicz died from his injuries. Officer Seng is currently recovering. 

"Justice will be served," Mayor Malik Evans said. "The thought that he could come and wreak havoc on the city of Rochester and get away with it - he will not get away with it. Rochester is a safer place with this individual off the streets."

Vickers pleaded not guilty at his arraignment in July, authorities say. He faces a maximum sentence of 25 years to life in prison if convicted, according to prosecutors.

“If the defendant is convicted of aggravated murder, the only possibility is life without the possibility of parole," Doorley said.

Vickers has a long criminal record dating to when he was 12 years old and accused of assault and battery on a police officer, said Doorley.

Doorley said Vickers’ juvenile record includes burglary, strangulation with a deadly weapon, assault with a deadly weapon, and two firearms offenses. As an adult, he served a prison sentence of 2 1/2 to 3 years for unlicensed weapons possession and was released by the Massachusetts Department of Corrections on May 24.

The district attorney weighed the charges -- murder in the first degree or aggravated murder.

“There was additional evidence that we presented to the grand jury and based on the evidence that we presented to the grand jury I decided to give them the option of voting the charge of aggravated murder," Doorley said.

The aggravated murder charge carries with it a mandatory life sentence without the possibility of parole. It is supported by evidence suggesting the shooter knew or should have known that Mazurkiewicz and Seng were police officers, Doorley said.

“The aggravated murder is the killing of a police officer in the line of duty and the allegations that the defendant knew or reasonably should have known that the individual was a police officer at the time of his actions," Doorley said.

Doorley says she believes there is evidence to support the aggravated murder charge.

She declined to discuss a possible motive for the July attack. Authorities have said the two officers were part of a plainclothes unit and were investigating a murder.

An hour after the shooting, Vickers was found in a nearby vacant house. He pleaded not guilty to initial charges of second-degree murder, attempted murder, assault and weapons counts and has been held without bail.

“He was not a Rochester resident. He was just released from prison. He was here and now he’s accused of killing a police officer,” Doorley said.

"Today is about justice for Officer Mazurkiewicz, Officer Seng and their families in this community," Monroe County Executive Adam Bello said. "Today is about sending a message that there are consequences for violence and murder. Public safety is fundamental to the future of the safety to our city and to our county. Our public safety is being challenged right now and we must answer that challenge with action...These shootings must stop and the shooters must face consequences."

“We have great work to do in our community to combat gun violence, but right now at this press conference today," Evans said. "I am just so pleased that this indictment has been served up and that justice will be serviced in this case.”

Doorley will personally prosecute this case.

Vickers is being held without bail, police say. The DA's office says he will be arraigned on these charges in Monroe County Superior Court on August 10 at 9:30 a.m.