Police are investigating after they found two people stabbed to death on separate New York City subway trains Friday night.
Shea said the four attacks occurred on the A line, a subway line that runs between northern Manhattan and Queens.
"To the victims, to the victims' families, we are 100 per cent committed to getting justice ... to bring closure to the families of this bad incident", NYPD Commissioner Dermot Shea said during the news conference.
NYPD Chief of Transit Kathleen O'Reilly said Saturday that at least three of the incidents appear to be connected and the department is looking into whether all four stabbings were committed by the same individual. That victim is recovering in a nearby hospital.
Officials say a man was discovered with stab wounds to his neck and torso aboard an A train around 11:30 p.m. Friday at the Mott Avenue subway station in Far Rockaway, Queens, WABC reported.
The second stabbing victim, a 44-year-old woman, was found lying under a bench inside an A train stopped at the West 207th Street-Broadway station in Inwood, Manhattan, around 1:20 a.m. Saturday, police said.
"This surge will result in an additional 500 officers, which is a significant increase in the staffing of our transit bureau, and they will be deployed immediately throughout New York City". She was also pronounced dead at the scene, according to the NYPD.
In a fourth incident early Saturday, a 43-year-old man was stabbed back at the West 181st Street station. He's in stable condition.
A police spokesperson said it's unclear if the deaths are connected.
"We had an incredible and total disruption in 2020, our entire lives are turned upside down, a global pandemic, a ideal storm", de Blasio said at a news conference Tuesday.
The heads of the city's transit system and transit workers union called the attacks "outrageous and unacceptable".
"We have been calling on the city to add more police to the system, and to do more to assist those who desperately need mental health assistance", Feinberg and Utano said Saturday.