A man wielding a long metal object rampaged through New York City early Saturday attacking sleeping homeless people, killing four and leaving a fifth in critical condition.
New York Police Department Detective Annette Shelton said the men were brutally assaulted in the city's Chinatown neighbourhood with the object that authorities recovered.
Police responded to a 911 call just before 2 a.m. as one assault was in progress.
A 24-year-old suspect is in custody but has yet to be charged, the detective said.
The victims apparently were asleep when they were attacked in three different locations. The first died of blunt trauma to the head. A second man was attacked nearby but survived. He was taken to New York Downtown Hospital in critical condition.
The other three victims, attacked about a block away, also died of trauma to the head.
The New York Post published photos of two of the victims under a white sheet, one slumped in a blood-spattered doorway. The other lay under a sheet on the sidewalk. The identities of the victims have not been released.
New York City's homeless population has grown in recent years, to a great extent because of the lack of affordable housing.
The killings started on The Bowery, which cuts through Chinatown and has for decades been known as New York's skid row, inhabited by homeless addicts and alcoholics.
During the day, the neighbourhood is bustling with small businesses and street vendors offering discount goods, its sidewalks packed with pedestrians.
Late at night, when the shops close, it turns into a quiet, desolate neighbourhood that was the setting for Saturday's attacks.