EL CAJON, Calif.—The investigation is continuing into the crash of a small airplane that took off from John Wayne Airport in Santa Ana and slammed into a neighborhood near El Cajon, killing all four people aboard. Multiple media reports indicated that the plane was operating as an air ambulance and that the victims were two pilots and two nurses. The crash was reported at 7:15 p.m. on Dec. 27 near the 1200 block of Pepper Drive and North Mollison Avenue in the unincorporated Bostonia neighborhood. The area is a few miles east of Gillespie Field airport, where the plane was scheduled to land. No information has been released about what led to the crash. The Federal Aviation Administration and National Transportation Safety Board will be handling the investigation. According to the safety board, the plane was a Learjet 35A business jet, which seats eight people. The aircraft belonged to an El Cajon company called Aeromedevac Air Ambulance, and had flown a …