Police were called just after 12.30pm after receiving a report of a robbery at Loyds bank in Queen Street.
Bogdan Popescu, 29, was using the ATM at the bank when he saw a grey Audi car park partially on the pavement in front of the bank.
Mr Popescu told the YEP: "I looked through the window inside the bank and I saw a man wearing a plain white mask and a grey boiler suit.
"He had a brown or rust shotgun. At first I thought it was a joke, then I saw a woman clerk behind the desk giving them papers or money."
Mr Popescu said he saw three men all dressed in plain white masks and grey boiler suits leaving tyhe bank. He said a fourth man was waiting in the Audi.
Mr Popescu said one of the three men he saw leaving the bank was carrying a small axe.
A West Yorkshitre police spokeswoman, said: "Officers are at the scene and enquiries are ongoing."
Waqar Ahmed posted a photo of the Audi on Facebookm and also a video of three men leaving the bank and climbing in to an Audi before it was driven off.