Firstly, also my condolances to the berieved.
I have often realised that my aircraft had begun to be refueled while passengers were still disembarkng and have mentioned it to dispatchers, refuellers and the companies for which I have worked. The result has been a slow head shake of pity for the eager beaver making trouble - me. `' Nothing can happen", I have often heard - now this.
The point is that to refuel in an orderly way with pax on board, quite a few parameters have to be met (see also above - from Australia) - including, usually a pax announcement and various exit rules, depending on company and airfield.
The crew can only run these items if they are INFORMED. An early refuelling during or even before disembarkation does not allow crew coordination, so whether the pax are going the right way or not, nothing is prepared and somebody's rules are for sure being broken.
OK, in this particular case, the passengers/crew remained unhurt but when you see the fuss which is made on a "normal " refuel with pax on board BEFORE a flight, then compare it to the laid back refueling which goes on AFTER a flight, some serious changes need to be implemented.