LAS CRUCES, N.M. (AP) — An air ambulance carrying a cancer patient to Phoenix crashed shortly after taking off from a southern New Mexico airport, killing all four people aboard, authorities said Thursday.The twin-engine aircraft had just left the Las Cruces airport on Wednesday evening and was reported by witnesses to be flying low when it hit a mesquite tree in a field, flipped and burst into flames, according to New Mexico State Police Lt. James Frietze.Tom Latson, an investigator with the National Transportation Safety Board, said it appeared the plane caught fire as it hit the ground.Crew members killed were identified as 29-year-old pilot Freddy Martinez, 27-year-old flight paramedic Tauren Summers and 35-year-old flight nurse Monica Chavez, all from El Paso, Texas. The patient was identified as 59-year-old Fredrick Green.Frietze said there weren’t any weather issues in the area at the time. Several witnesses reported the plane was flying low before it crashed on federal land surrounded by mesquite trees about 10 miles outside Las Cruces.Green’s 55-year-old brother, Leslie, said the elder Green was living in the Phoenix area when he was diagnosed with a brain tumor.