A deranged Hamptons man stabbed his wheelchair-bound mom more than 40 times before horrified cops opened fire to stop the vicious Mother’s Day attack, officials revealed Monday.

Steven Eastwood, 28, was shot and killed by cops during the shocking Sunday afternoon attack, which has the elderly victim fighting for her life at a local hospital and three police officers “very shook,” Southampton police Chief James Kiernan told reporters.

“There have been numerous incidents at this address over the last decade,” Kiernan said at a press briefing Monday. “Faced with an ongoing, deadly assault, officers discharged their serve weapons, striking Mr. Eastwood and immediately stopping the attack.”

Police said the nightmarish set of events began to unfold shortly before 2:45 p.m., when the unidentified victim made a frantic 911 call from her Toppings Path Drive home in Northampton to report that her son was intoxicated and acting violently.

The disabled mom made a second 911 call as cops raced to the scene, this time telling the dispatcher that her out-of-control son was now threatening her with a knife.

When the officers arrived they found Eastwood standing over his blood-drenched mom, still wielding a knife.

Eastwood ignored repeated demands by police to drop the weapon and instead turned on his mother again and continued to slash her — forcing the three cops to open fire, Kierney said.

Miraculously, the victim survived and is now fighting for her life at Stony Brook University Hospital.

The woman has three sons who are triplets, two of them suffering from mental illness, and police said the family has a history of domestic violence dating back almost a decade.

The victim had an order of protection against her son in the past but it was no longer active.

Kierney said the three officers were transported to the hospital to be evaluated for trauma, with the chief describing them as “doing okay, but very shook.”

Police did not reveal a possible motive for the Mother’s Day attack.

The state Attorney General’s Office is now investigating the shooting, which is standard procedure for all police-involved fatalities in the Empire State.

“Yesterday’s incident was extremely tragic and violent,” Southampton town Supervisor Maria Moore said Monday. “Our concerns, first and foremost, are the victim and her family as she continues to fight the very serious injuries.

“We’re grateful for the rapid response of, and the professionalism demonstrated, by our police officers, EMS personnel, and assisting agencies during a dangerous and rapidly evolving situation,” she said.