A 24-year-old suspect who is homeless is in custody, but has not been charged.
Police said he was found near one of the crime scenes in possession of a metal pipe.
The victims were brutally assaulted in the city’s Chinatown neighborhood in Lower Manhattan in three different locations, police said.
The assaults appear to have been "random attacks," and the victims were apparently sleeping at the time they were assaulted, police said.
Officers first responded to reports of an assault around 2 a.m. and found an unconscious man lying in the street with severe head trauma. He was pronounced dead at the scene.
Related: Vintage crime photos from the Daily News
Vintage crime photos from the Daily News
Vintage crime photos from the Daily News
UNITED STATES - MARCH 03: Confessed Slayer Enraged. William Patrick Farrell screams as he lunges toward fotog taking his picture in van outside Police Headquarters. Police say that Farrell, 25, father of two, reenacted for them the slaying of NYU coed Ann Yarrow last month. Farrell, a patient at Bellevue Hosipital twice before, was ordered to Bellevue again. (Photo by Al Amy/NY Daily News Archive via Getty Images)
UNITED STATES - MARCH 25: Leon Liss, Barney Mortillaro, Milton (Shuffles) Goldberg, Louis Liss, Pasquale Chicarelli and gang leader Richard Reese Whittemore (l. to r.) in a police lineup, after they were implicated in a gem holdup on W. 48th St. (Photo by NY Daily News Archive via Getty Images)
UNITED STATES - JANUARY 09: Theodore A. Clement in the back of a police paddy wagon after allegedly shooting a man during a poker game. (Photo by Al Amy/NY Daily News Archive via Getty Images)
UNITED STATES - JANUARY 20: Isadore Strauss in jail cell at police headquarters after his arrest for murder and robbery in connection with Whittemore gang job. (Photo by Paul Levine/NY Daily News Archive via Getty Images)
UNITED STATES - NOVEMBER 04: Abe (Kid Twist) Reles (center) in a police mug shot. (Photo by NY Daily News Archive via Getty Images)
UNITED STATES - CIRCA 2000: Liquor store owner Abraham Weissman views the body of stickupman, Otis Mims, whom he shot during an attempted robbery. (Photo by Gary Kagan/NY Daily News Archive via Getty Images)
UNITED STATES - SEPTEMBER 01: Mass murderer Harry F. Powers, the Butcher of Clarksburg, tells a detective about the details of his grisly murders in Clarksburg, W.Va. (Photo by NY Daily News Archive via Getty Images)
UNITED STATES - OCTOBER 19: Nela Bogacki, alias Nella Bogart, madam of the 'Continental call girl ring,' handcuffed to Salema Hontover after being seized by the F.B.I. Both are to be deported for illegal entry. (Photo by Al Amy/NY Daily News Archive via Getty Images)
UNITED STATES - OCTOBER 25: The body of Albert Anastasia - who ran Murder, Inc., a gang of hired killers for organized crime, in the late 1930s - lies on the barbershop floor at the Park Sheraton Hotel, Seventh Avenue and West 55th Street, soon after his murder by two gunmen at 10:20 A.M. (Photo by NY Daily News Archive via Getty Images)
UNITED STATES - APRIL 20: A manacled LeRoy Luscomb is charged with first degree murder in the killing of his wife with a deer rifle. His wife is on the bed in the rear of the photo., (Photo by NY Daily News Archive via Getty Images)
(Original Caption) When John Kerr, of 147 W. 84th Street, and Peter Macon, 490 Columbus Avenue, were being booked on a mugging charge at the West 68th St. Precinct today, photographer Phil Grietzer, New York Daily News photographer, drew a bead on the proceedings with his camera. He didn't know the boys had a camera allergy. But he found out when the two, although handcuffed together, came charging at him. Another photographer who doesn't suffer from buck fever, got this picture.
UNITED STATES - DECEMBER 16: Driver and bodyguard Thomas Bilotti lies on the street next to car after he and crime boss Paul Castellano were shot to death outside East Side steakhouse. (Photo by Thomas Monaster/NY Daily News Archive via Getty Images)
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They were later approached by another male with head trauma, assistant police chief Stephen Hughes said in a statement Saturday morning. He was taken to a hospital in critical condition, police said.
Two witnesses told officers that a man dressed with a black jacket and black pants repeatedly struck one of the victims in the head with a metal object, according to Hughes.
Shortly afterward, authorities "observed a male fitting the description carrying a metal object."
Hughes said officers took the man into custody and "recovered the metal pipe without further incident."
About two hours later, police found three additional men dead a few blocks away. They had also died of head trauma injuries, police said.