NEW YORK (CBSNewYork) – The homeless man accused of killing four other homeless men in Chinatown returned to court on Monday.

Investigators charged 24-year-old Randy Santos with four counts of murder.

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Santos pleaded not guilty.

Police say on Oct. 5, he used a metal pipe to beat five homeless men as they were sleeping on Bowery and East Broadway. Four of the five victims died.

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Investigators believe the attacks were random.

Santos is also charged with the attempted murder of the one man who survived the attacks and assault for another beating a week earlier.

He is being held without bail in the psychiatric prison ward at Bellevue Hospital.

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The rampage prompted Mayor Bill de Blasio to order the NYPD to review the city’s mental health services.