The incident took place shortly after 9pm on Saturday at a store on Hawthorn Street in North Glasgow.
Police say a man entered the premises at this time and sprayed a staff member with a substance before making off with a sum of cash.
Emergency services rushed to the scene, and the employee, a 24-year-old man, was taken to Glasgow Royal Infirmary for treatment.
His injuries have been described as “serious”.
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The suspect is described as white and of slim build.
He was wearing a green and grey tracksuit top with a zip, orange shorts, black socks, and black trainers.
Cops say he ran off in the direction of Memel Street.
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Detective Sergeant Greg Turnbull said: “This was an extremely frightening experience for the shop worker, which left him with serious injuries requiring hospital treatment.
“Extensive enquiries are ongoing to trace the man responsible, and we are asking anyone who knows who he is or where he might be to get in touch.
“We are also asking anyone who saw anything before or after the robbery to make contact.
“Please also check private CCTV and dash-cam footage to see if you have captured something that could assist with our investigation.”
Anyone with any information is urged to contact police on 101, quoting incident number 3850 of Saturday, August 16, 2025.
Alternatively, information can be passed on anonymously by contacting Crimestoppers on 0800 555 111.