The National Transportation Safety Board issued a preliminary report Friday after three people were killed in a medical helicopter crash in Madison County.The March 10 accident involved an AirCare helicopter that crashed in a highly wooded area near Canton. The commercial pilot, Cal Wesolowski, flight paramedic Dustin Pope, and flight nurse, Jakob Kindt, on board were all killed.The crew was flying back to Columbus after transporting a patient to St. Dominic-Jackson Memorial Hospital. They stopped to refuel the helicopter at University Mississippi Medical Center heliport.After getting back airborne, the pilot communicated to air traffic control at Jackson-Evers International Airport that it was "clear to the north" before ending communication five minutes before the crash.The helicopter flew over the Ross Barnett Reservoir and remained south over the Natchez Trace Parkway. After flying over the Pearl River State Wildlife Management Area, the helicopter began to descend.About halfway through the descent, the flight nurse called over the radio, saying, "We've got a major problem. We are having an emergency landing in a field right now. Ops are not good. Controls are giving us a lot of trouble, coming in fast."The NTSB report said there were no further radio transmissions.Data indicates the helicopter hit multiple trees during its descent. The wreckage was destroyed by a post-impact fire that burned for about three hours. Due to the remote location of the accident site, fire department units had to deploy 1,300 feet of hose after the initial fire suppression, which was carried out using tank water.A witness said they did not see any smoke or fire coming from the helicopter before it went down, but they heard a loud boom, yet did not hear the engines while the helicopter was airborne.The helicopter, which was manufactured in 2012, passed an inspection just hours before the crash, according to the NTSB.