HEMPSTEAD - Police say a woman was sexually assaulted during a Hempstead home invasion last night. According to police, three men with a gun and knives pushed their way into an apartment on Grove Street at around 11 p.m. The suspects ran upstairs and robbed a 44-year-old woman of her cash and cell phone, before two of them simultaneously sexually assaulted her, police say. Investigators say the woman's sister witnessed the attack and tried to escape from a second-floor window. Slightly injured, the woman slowly made her way next door and knocked for help, asking the neighbor to call police.Meanwhile, police say the masked intruders were attempting to tie up a third woman when she started having a seizure. They realized one of the women had escaped and seconds later were spotted fleeing on foot down the street, authorities say. Anyone with information is urged to call Nassau Crime Stoppers at 1-800-244-TIPS.