Indianapolis police are investigating reports of two fatal stabbings in the city early today.About 2 a.m., officers arrived at a home in 2936 Schofield Ave., where a man had called police to say he had stabbed his grandmother. Investigators found a 77-year-old woman with several stab wounds in her neck, said Sgt. Matthew Mount. She died about an hour later at Wishard Memorial Hospital, Mount said.Mount identified the victim as Marian Cobb and said her grandson, grandson, Bryan Torrence, 20, also of that address, has been arrested for murder.A 20-year-old man is in custody on a preliminary charge of murder.In the other incident, IMPD officers were sent to the 1100 block of South Keystone Ave. about 2:25 a.m., also on a report of a stabbing. Randy J. Woodyard, 43, was found dead at the residence, where he had been staying. Police said they later found a woman described as the man’s girlfriend, Kelly J. Pappas, 38, at 1030 Churchman Ave., where she was arrested on a preliminary charge of murder.Police say an argument between the two escalated into a fight, during which Pappas stabbed Woodyard in the chest.Additional details are pending in both homicides.