Phoenix police are investigating three serious traffic collisions that occurred in separate incidents between Saturday night and Monday evening, leaving two people dead and one critically injured. The most recent crash happened shortly after 8 p.m. on Monday near 36th Street and McDowell Road, where officers found an unresponsive boy who had been struck by a car. He was taken to a hospital in critical condition and later died. Investigators said the adult driver remained at the scene, and they have not yet disclosed whether impairment or speed contributed to the collision. On Sunday, a woman was struck and killed by a vehicle in central Phoenix. Authorities have not released her identity or details about the driver. Late Saturday night, a motorcyclist suffered serious injuries in a hit-and-run near 35th and Dunlap avenues; police are still searching for the driver involved. All three investigations remain open as detectives review evidence and interview witnesses. The police department has urged anyone with information, particularly about Saturday’s hit-and-run, to come forward.