A man slit the throat of a woman who was baby-sitting her two grandchildren, sexually assaulted one of the children, then barricaded himself inside their Long Island home for 14 hours before shooting himself on Monday, police said. The woman who lives at the home returned around 12:30 a.m. and found her 59-year-old mother dead in a pool of blood in the garage, police said. Phillip Zagarella, 50, looming in a doorway with a rifle, yelled for the woman to get inside, but she ran to a neighbor's home and called police to say her two children, ages 10 and 13, were still inside, Detective Lt. Jack Fitzpatrick said. The children were let go a few hours later. Police did not release any information on their condition.