"A search was commenced by responding staff but it was somewhat difficult to do given we didn't have a description of the offenders and only a partial description of one of the two vehicles used by the offenders to escape in."
One of the vehicles was described as a fish truck which police have narrowed down to be a utility with a chiller unit on the back.
"Given the offender armed with the pistol was hit with some force by the victim's walking stick he may have suffered an arm injury, possibly even a broken arm and we're asking any medical centre in the area who may have treated someone for such an injury to contact us.
"It goes without question this incident is being treated very seriously by police and we must reiterate the warning that unless absolutely necessary do not aggravate the situation and be compliant and if any opportunity arises for you to escape, do so, its better to flee than fight."
Mr Hughes said in the interim police want to hear from anyone who may have information on what may have happened.
"You can speak to the enquiry team directly by calling Thames Police on 07 8679600 or alternatively you can leave information anonymously with Crimestoppers on 0800555111."