The man charged in the massacre of four sleeping vagrants in Chinatown is now suspected in another attack on a homeless man about a week earlier, the NYPD revealed Tuesday.

Surveillance video shows Randy Santos, 24, about seven blocks from where a victim was awakened by an assailant beating him with a stick near Chelsea Pier on Sept. 27, Chief of Detectives Dermot Shea said.

The evidence, combined with Santos’ alleged confession in Saturday’s deadly bludgeoning spree, has led cops to “believe he was responsible for that attack,” Shea said during an unrelated news conference in Queens.

In addition to being battered, the victim told cops that he was pushed against a railing in an attempt to force him into the Hudson River, but managed to fight off his assailant, Shea said. The victim suffered cuts to his chest and is hospitalized in stable condition, according to Shea.

NYPD officials urged anyone with information about similar incidents to report them.

Authorities have identified the last of the four men bludgeoned to death Saturday, but are withholding his name pending notification of next of kin. A fifth victim in Saturday’s rampage was recovering in a hospital.

Santos had been scheduled for a hearing Tuesday morning in Queens Criminal Court over a March 8 groping incident in a homeless hotel, but his lawyers waived his appearance pending another hearing Nov. 6.

Hours earlier, The Post exclusively revealed that the nonprofit Bronx Freedom Fund paid Santos’ $1,000 bail in that case Aug. 12, putting him on the streets before Saturday’s bloodbath.