Police fatally shot a man who viciously stabbed his disabled mother at their Long Island home on Mother’s Day, according to authorities and sources. Southampton cops responded to an “escalating domestic situation” at a Riverhead residence on Topping Drive around 2:40 p.m. on Sunday, according to the Suffolk County Police Department. Police fatally shot a man who allegedly stabbed his disabled mother at their Southampton home on Mother’s Day. ABC 7 The mother, who sustained several stab wounds in the harrowing attack, was rushed to a local hospital with serious injuries. ABC 7 When officers arrived at the home, they found the son actively stabbing his mother, sources said. The unidentified man was shot and killed by officers with the Southampton Town Police Department after he refused to put down the knife, according to sources and police. The mother, who sustained several stab wounds in the harrowing attack, was rushed to a local hospital with serious injuries, sources and cops said.…