Mayor Eric Adams said all of the victims were transient and alone at the time they were killed.
Berta Landi says her younger brother was as a hard worker, responsible, friendly and always willing to help others in need.
She showed up to court on Tuesday afternoon holding a picture of Angel Landi, and demanding justice for her only brother.
"I need justice for my brother, I don't want his death to be in vain," she said.
Landi was the first of three killed Monday morning -- allegedly at the hands of Ramon Rivera.
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Police say 51-year-old Rivera stabbed the 36-year-old on West 19th Street around 8:30 am. as he was heading to work as a construction worker.
He was an Ecuadorian migrant living in a Peekskill rooming house. There is now a growing memorial where he was killed.
"A hard-working man in construction was stabbed by a mentally ill person, and then we find out that he was freed eight times, so why did the system let this criminal walk out of the justice system?" said Walter Sinche with Ecuadorian International Alliance.
About two hours later, police say Rivera made his way to East 30th Street where he stabbed and killed 67-year-old Chang Wang who was fishing.
A single candle now marks the spot.
Then at 10:55 a.m., police say Rivera stabbed and killed his last victim, Wilma Augustin near the U.N. at East 42nd Street and 1st Avenue.
The 36-year-old lived at a migrant shelter on West 38th Street and has an 8-year-old son.
Rivera's case is renewing frustration with the city's inability to treat people in mental distress and hold people with a history of low-level criminal activity.
Adams said legislation strengthening the power to involuntarily remove troubled homeless people from the streets will be a priority in Albany next session.
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