The New York City Police Department said the suspect shot and killed one homeless man and wounded another in separate street attacks Saturday morning.
The Metropolitan Police Department in Washington D.C. also announced Sunday night they are looking for the same man.
The incidents in the nation's capital occurred between March 3 and March 8. One of the victims in D.C. was shot and stabbed, then set on fire. He later died.
Between the two cities, there have been five shootings and two homicides.
Police in NYC said a sleeping victim was shot in the right arm in the SoHo neighborhood at approximately 4:30 a.m. Saturday. He was transported to Bellevue Hospital and listed as stable.
According to police, security video showed the suspect, wearing all black and a black ski mask, approaching and shooting a man in a sleeping bag about 10 blocks away and 90 minutes after the first attack. Police found the victim at approximately 4 p.m. Saturday and he was pronounced dead at the scene with a gunshot wound to the head and neck.
"The case is a clear and horrific intentional act of taking the life of someone, it appears, because he was homeless," Mayor Eric Adams said at a news conference. "Two individuals were shot while sleeping on the streets, not committing a crime but sleeping on the streets."
Police also said another homeless person was fatally shot on Murray Street in the city's TriBeCa neighborhood Sunday night. Detectives are trying to determine if this shooting is linked to the suspect.
A $10,000 reward is being offered in the case.
Anyone with information on the identity of the male suspect is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
The public can also submit their tips by logging onto the CrimeStoppers website at nypdcrimestoppers.com or on Twitter @NYPDTips.
Teams are currently also reaching out to homeless populations in Newark, New Jersey to alert them of the shooter.
The Associated Press contributed to this report.