From what I hear it was a helicopter R44 from Juba to Tanzania, which stopped off in Wilson for fuel and also some technical issues. It was doing some short test flights or it was repositioning for fuel - depending on the story - when it either had a problem or the pilot lost control and it dropped to the ground, falling over on impact. This was right between AirKenya's hangar and the control tower.
Some brave individuals pulled the two crew out of the helicopter, which slowly began to burn. The Wilson Airport fire engine attended, but didn't have enough water/water pressure/foam retardent so when they poured water on the burning avgas the fire spread rapidly. Airkenya staff nearby grabbed their emergency fire extinguishers and attempted to put out the fire. By now however it was burning too much and whatever was left of the heli was reduced to a pile of ashes/tail only.