Philippine police say they have arrested the alleged gunman and two other suspects in connection with the killing of a distinguished American marine biologist in his house in the central Philippines. Three men broke into the house of Kent Carpenter, 73, in the coastal town of Sibulan in Negros Oriental province on Sunday and one shot him in the head with a handgun as he sat on a sofa, police officials said. “It was really a planned robbery,” national police spokesperson Col. Allen Rae Co said. “So, we are still verifying why they killed the American marine biologist.” A fourth suspect is still being hunted.