NEW YORK (AP) — A man has been charged with three counts of first-degree murder in the fatal stabbings of three people in a string of random attacks in Manhattan, police said Tuesday.

Ramon Rivera, 51, was arrested after he was found with blood on his clothes and two kitchen knives, authorities said.

“Three New Yorkers. The unprovoked attacks that left us looking for answers as to how something like this could happen,” Mayor Eric Adams said at a news conference Monday afternoon.

Investigators were scrambling to understand what set off the altercation, which happened over two and a half hours on Monday.

“No words were exchanged. No property taken. Just attacked, vicious,” said New York Police Department Chief of Detectives Joseph Kenny. “He just walked up to them and started attacking them with the knives.”

The first stabbing, on West 19th Street, killed a 36-year-old construction worker, Angel Lata Landi, who was standing near his construction site near the Hudson River shortly before 8:30 a.m., police said. About two hours later and across Manhattan Island, a 68-year-old man was attacked while fishing in the East River near East 30th Street.

Both men died shortly after the stabbing, Kenny said. The fisherman’s name was not immediately released.

The suspect then reportedly traveled north near the river bank. Around 10:55 a.m., a 36-year-old woman identified as Wilma Augustin was stabbed multiple times near the United Nations headquarters on East 42nd Street, Kenny said. She died later Monday at a hospital, police said.

A passing taxi driver saw the third attack and alerted police at nearby First Avenue and East 46th Street, officials said. An officer soon apprehended the suspect.

Rivera was arraigned Tuesday. The Legal Aid Society, which is representing Rivera in court, declined to comment.

The bloodshed took place in a major city where, as in others, crime has figured prominently in political discourse and everyday concerns in the years since pandemic lockdowns have emptied the streets and fueled disorder. Homicides in New York so far in 2024 are down 14 percent in two years, but serious assaults are up about 12 percent, according to police statistics.

Some recent stabbings in public places have drawn attention, including a fatal one attack at the Coney Island subway station just a few weeks ago.

Adams, a Democrat, called Monday’s violence “a clear and stark example” of failures in the criminal justice system and elsewhere.

The suspect in Monday’s rampage, who is apparently homeless, had been convicted in a criminal case several months ago and was arrested in a grand larceny case last month, officials said.

The fury came three years after a string of stabbings at various points along a subway line killed two people and injured two others within hours.

In 2019, four people who were sleeping in doorways and sidewalks in Chinatown were beaten to death, and a fifth was seriously injured, early on a Saturday morning.