He was angry because he did not have enough money in his bank account.
According to blikk.hu, he threatened the employees of a 7th district bank that he would blow the building up. He was angry because they were not able to give them the required amount of money.
He went away but returned shortly afterwards, claiming even more money. When the employees told him he did not have the coverage, he
threatened them again.
However, this time the security guard of the bank kept him inside until the police arrived. He did not have any weapons or explosives, but the police will bring the issue to court.