A cash and carry employee is fighting for his life after he was blasted in the chest with a shotgun as he tried to stop a gang of armed robbers.
Colin Thomas, 24, was shot at point-blank range during the raid at a branch of Costco, in Croydon, south London.
A gang of five masked raiders wearing hoods and scarves ran into the busy warehouse store at about 7.40pm on Thursday and made off with a haul of jewellery after smashing several glass cabinets with a hammer.
Alerted by an automatic alarm, Mr Thomas ran to stop them but was shot by one of two men guarding the main exit.
Colleagues described Mr Thomas, recently promoted to supervisor, as a "phenomenal" worker and "role model".
Detective Superintendent Bob Cummings, of the Flying Squad, said Mr Thomas probably reacted "instinctively" after hearing the alarms and seeing the commotion.
Mr Cummings said Mr Thomas underwent emergency surgery and was in a serious condition.
"We are very concerned about him. Costco employees are very concerned about him and his family are with him.
"He has worked for Costco for five months and has already been promoted in that short time.
"He is an intelligent man who acted extremely courageously on this occasion.
"It is very sad (that) a man just carrying out his job should have this happen to him."
Mr Cummings said it is not yet known how much the stolen jewellery was worth. He declined to give further details.
Sources close to the store said the total value of the missing jewellery could be hundreds of thousands of pounds.
It is believed to include a large number of Rolex watches and expensive gold, platinum and diamond rings.
The officer said five men - described as black and wearing hoods and scarves - ran inside the store.
He said two stayed by the door and the other three raided the jewellery cabinets - activating an alarm - before heading for the exit.
Staff pursued them towards the exit where Mr Thomas was confronted by one of the two men guarding the door.
"That man has fired a shot with a shotgun at point-blank range," he said.
The men fled towards playing fields on Purley Way.
Police said the the area would have been busy on Thursday evening and are appealing for witnesses to contact them.
The senior detective said the men are likely to have visited the store before to plan the robbery.
"If you were planning a jewellery robbery Costco is probably not the first place you would choose.
"By the two men remaining by the door, because the display cabinets are not by the door, would suggest they have undertaken planning reconnaissance in the past."
Police have seized CCTV footage and are examining images from other companies on the business estate.
Store manager Martin Sandler said of Mr Thomas: "He was a role model, a phenomenal worker. He had just been promoted to supervisor."
Asked about his condition, he replied: "He is not out of the woods yet."
A fellow Costco employee added: "Our thoughts are with our colleague who was injured and remains in hospital. We are just hoping he makes a full recovery."
:: Anyone with any information is asked to call the Flying Squad on 0207 232 5630 or Crimestoppers on 0800 555 111.