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. 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