At the High Court in Glasgow, Darren Timothy and a 16-year-old and a 14-year-old, who cannot be named for legal reasons, admitted attempting to murder Atiq-Ur Rehman at the Glenhove Store.
Co-accused Kieran Ruddy (20) admitted assaulting Mr Rehman by kicking and punching him on the head and body.
Mr Rehman was stabbed three times and suffered a fractured shoulder in the attack which was caught on the convenience store’s CCTV and shown to the court.
The gang entered the shop at 7.50pm on December 24, the 16-year-old kicked Mr Rehman on the body and repeatedly struck him with a knife.
The group jumped over the counter to steal alcohol and continued assaulting Mr Rehman. The 16-year-old restrained the victim while the three others punched and stamped on his body, while also kicking and punching him on the head.
They left the shop, but came back and further assaulted Mr Rehman again before finally leaving.
A passer-by overheard one of the accused boasting about stabbing Mr Rehman and dialled 999. He was treated at Monklands Hospital in Airdrie for five days.
The court heard if it were not for the medical treatment Mr Rehman could have died from his injuries.
Judge Lord Mulholland deferred sentencing until next month and the four were remanded in custody.
The judge said: “You behaved like a pack of wild animals to a man that was just serving the community.
“What you subjected him to was nothing short of a disgrace.”