Robbers escaped with a five-figure sum of cash when they targeted a Dundee business at closing time.
A 61-year-old man was attacked by two men as he was locking up the Wing Fung Cash and Carry in the Wester Gourdie Industrial Estate at 2010 GMT.
They stole a black nylon briefcase bag with a Red Cross-style symbol, which contained the cash, bank cards, cheque books and keys.
The men ran to Liff Place, where a vehicle was waiting to pick them up.
Police said they were examining whether the getaway car had been parked in Camperdown Park, and whether the men had been in the park before the robbery.
Detectives want to speak to anyone who was driving in the Liff Road area at the time of the incident.
This includes the driver of an articulated lorry with a dark-coloured cab and a light-coloured trailer which was seen parking on Liff Road.
Det Insp Kevin McMahon said: ''It's highly likely that the driver would have seen the two men responsible for this incident.
''A number of cars are seen to drive eastwards along Liff Road around the time of the incident and I'd ask those drivers to get in touch with us as they may have vital information for the inquiry team.
''The 61-year-old man was not physically injured as a result of the incident but has been left extremely shaken."
The attackers were both said to be aged between 20 and 30 and were about 5ft 10in tall.
One was wearing a dark grey hooded top with reflective markings, while the other was wearing light coloured clothing.