Police were able to make a routine arrest when they arrived at the bank at Wieselgrensplatsen and found the robber being held down by customers.
The robber was described by witnesses as skinny and wearing a hooded top.
“The robber came in, pulled out his gun and went up to the cash desk. Then he said: ‘Take it easy – this is a robbery’,” one witness told newspaper GT.
There were chaotic scenes in the bank when several customers jumped on the man, who is said by witnesses to have fired three shots.
Police said they were not certain whether the man had fired live ammunition or blanks.
One man was left requiring treatment for a hand injury, which police said was not a gunshot wound.
A number of witnesses were interviewed by police on Friday afternoon. The floor of the bank was still covered in bank notes more than an hour after the attempted robbery.