After coaching my boy for quite some months on the essence of writing, below is the one which he has done it without my help. I would say it's a good attempt and here it is with his permission. Yes, there is definitely room for improvement but it is quite a job well done.
It was a beautiful day. The bank had just opened for business. Two robbers were lurking outside the bank. They were behaving suspiciously. As soon as the security guard had left for lunch, they entered the bank.
Once inside the bank, they took their weapons and ordered everybody to kneel down and put their heads on their head. They threatened, "Whoever moves will die!" The people in the bank were terrified. They trembled with fear. The robber who was armed with an axe, shouted at the cashier, "Hand over all your cash. If you do not do as I say, I will kill you with this axe!" The other robber who was armed with a sharp knife, stood guard over the customers.
A passer-by looked into the bank and realised that there was a robbery going on in the bank. He quickly went to the nearest telephone booth and dialled "999".
Within minutes, the police arrived at the bank. They dashed into the bank and caught the robbers red-handed. The robbers were taken by surprise. The police arrested the robbers and handcuffed them. The police brought the robbers bank to the police-station.