Police investigating a series of murders in New York City have confirmed that the horrific crimes are linked to a similar murder spree in Washington D.C.

The chilling crimes began March 3 when the Metropolitan Police Department of D.C. responded to a call around 4 a.m. and discovered that a homeless man had sustained a gunshot wound. He was treated at a hospital and survived the injuries.

Five days later, another person was found shot in the early hours of the morning and survived. The following day, a similar attack proved fatal.

Around 3 a.m. on March 9, responders discovered a body inside a burning tent northeast of the city’s center. After extinguishing the flames, investigators discovered that the person, formerly homeless, had been shot and stabbed.

The D.C. police confirmed that all three victims had been experiencing homelessness—and all three had been targeted by the same suspect.

The murder spree then took an escalating turn for the worse when three more homeless people were attacked over the weekend. This time, the victims were in New York City.

NBC 4 reports that the first two attacks, one in Tribeca and another in Chinatown, occurred less than two hours apart early Saturday morning. Surveillance footage captures a suspect, clad in black, approaching a man asleep on a sidewalk in a yellow sleeping bag. The assailant checks his surroundings and nudges the sleeping figure with his foot. He then pulls a gun from his pocket and fires.

Investigators were able to confirm that this shooter in lower Manhattan also committed the attacks in D.C.

As in D.C., the threat to New York’s homeless community didn’t stop there.

On Sunday evening around 6 p.m., a third man was shot, also fatally, in Manhattan, this time near Greenwich and Murray streets. NYPD officers told CBS that they knew the victim, who was 42, and had last spoken with him the morning of his death. Though this third attack occurred within the vicinity of the prior shootings in Manhattan, police have not confirmed that it was committed by the same perpetrator.

In a statement, the Metropolitan Police of D.C. announced that it is working together with NYPD and the Bureau of Alcohol, Tobacco, Firearms and Explosives to find the killer responsible for at least five shootings that have left two homeless people dead.

“Our homeless population is one of our most vulnerable, and an individual preying on them as they sleep is an exceptionally heinous crime,” New York City Police Commissioner Keechant Sewell said in the statement. “We will use every tool, every technique, and every partner to bring the killer to justice.”

As investigators work to identify and catch the interstate serial killer, officers and outreach workers are reportedly scattering throughout New York City to warn the homeless community to find protection and shelter if they can.