Gerald Brevard this is the 30-year-old perpetrator

As part of a joint investigation with the New York Police Department, several photos and videos of the suspect were posted on social media, and on Tuesday morning, Washington DC police said they had arrested him.

"Earlier today, law enforcement arrested the suspect in Washington, DC. He is currently being questioned in our homicide unit," the agency tweeted. "More information will be released shortly. Thank you to the community for all your tips."

A senior law enforcement official identified him to NBC News as 30-year-old Gerald Brevard.

He has a criminal history, including an alleged assault on a woman in Virginia, they said.

Investigators did not say what led them to him; the reward offered by all authorities searching for him totals $70,000.

A harrowing video shows a suspect executing a homeless man in his sleeping bag - and it wasn't his first victim, according to police.

The gruesome footage shows the killer shooting the victim in the head at close range Saturday morning while he slept in a doorway. Investigators believe the gunman is responsible for a string of murders and attempted murders of homeless people in two states.

Around 4:30 a.m. Saturday morning, police say another 38-year-old homeless man was shot in the arm as he slept at the corner of King St. and Varick.

"The victim woke up ... ... and yelled, 'What are you doing?"' NYPD Deputy Chief Hank Saunter said at a news conference, adding that the perpetrator then fled the scene. But he didn't flee far, nor was he dissuaded from his grim mission.

"Today, around 4:30 p.m., police responded to a 911 call about a person in need of assistance in front of 149 Lafayette Street. When officers arrived, they found an unconscious and unresponsive male person in a sleeping bag," the deputy chief said. "The unidentified man had sustained a gunshot wound to the head and neck. Paramedics pronounced him dead at the scene."

Video surveillance shows the second victim was shot at 6 a.m. and had been there for nearly 11 hours before anyone became aware.

The two shootings occurred less than a mile apart.

The terrifying footage shows the masked suspect standing over the sleeping victim, nudging him with his foot and looking around to see if anyone was watching before pulling out a gun and firing several shots at close range.

"We're dealing with two homeless people here who are the most vulnerable population in the city right now," Deputy Chief Saunter said.

The first victim was of Hispanic descent, the second was black; investigators do not believe race was a motive.

Mayor Eric Adams said the two victims were targeted only because they were homeless; "they weren't committing a crime, they were sleeping on the streets."

"I'm here today to send a very clear message: All New Yorkers matter," he said.

"When you look at the video and you see someone intentionally walking up to innocent people who are struggling with the challenges of homelessness, it's very possible that one of our citizens is still alive just because they woke up."

"A total breach of trust," he added. "The video is terrifying. To see a cold-blooded act of murder. Homelessness turning into murder."

But worse was to come: on Monday morning, the NYPD announced that it also charged the suspect with three other shootings of homeless people in Washington DC - one of which resulted in death.

On March 3 at 4 a.m. and March 8 at 1:21 a.m., police say two other men were shot in Washington DC, but both survived.

On March 9, police called to a tent fire found the body of a homeless man. An autopsy revealed that he had been stabbed and shot.

Given the similarity of the perpetrator's modus operandi, the common circumstances in each shooting, the circumstances of the victims and the information from ATF's National Integrated Ballistic Information Network, we will continue to jointly investigate these murders and shootings," it said.

"Our homeless population is among the most vulnerable, and when someone assaults them while they are sleeping, it is an especially heinous crime," Police Chief Keechant L. Sewell said in the release.

Police are also investigating whether other homeless people were also targeted in unreported attacks.

The NYPD is offering a $10,000 reward for tips leading to a conviction.

"Demonizing the homeless is the wrong mindset," Mayor Adams said at the conference. "By the grace of God, I'm here."

"These are our brothers and sisters who have fallen on hard times. We have an obligation to provide them with the services they deserve."