VIDEO: Two investigations are happening Friday in a single, fifth floor apartment on 42nd Street in Sunset Park. Police said they responded to a report of an assault in the apartment building at around 4 p.m. Friday after a man was accused of using an unidentified weapon to slash a woman, his domestic partner, on her hand. When the woman's daughter went to go help, the man allegedly stabbed her, too – twice in the shoulder, police said. Investigators said the man then went into another room, set a mattress on fire, and then stabbed himself in the stomach. It is unclear what started this family dispute, but a neighbor who lives one floor below the family told PIX11 they were shocked to hear the news of such a disturbance. Fortunately, none of the injuries are life threatening. The mother and daughter were taken to an area hospital. The father was taken to a different hospital and is under arrest.