We don't know if the incident was just after land, before or after fueling etc.
So anything is pure speculation.
The pilot /s were arrested on suspicion of murder.
Could it be that they had had an altercation during fueling, the deceased had tried to stop the gyro copter from taxiing, by blocking the taxyway.
The pilot then manoveared his vehicle in an aggressive manor, striking the pedestrian.
Hence the suspicion of murder, especially if it was witnessed by other people.
Taking sides at this stage is ridiculous. As is my scenario, I am just trying to point out that there are only 2 facts. A man is dead and there was a gyrocopter. We don't even know for sure that the two had an interface.
So save your girlie bleating.