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 service weapons, striking Mr. Eastwood and immediately stopping the attack.” Police said there was a history of domestic violence at the Northampton home where Steven Eastwood was shot.…