A "feral" gang of youths was caught trying to smash its way into a supermarket with a fire extinguisher.
Aldi workers defended terrified shoppers from the gang by locking the doors - and belting one of the attackers.
Ross Scott was shopping in the store in Ruislip, west London, when as many as 10 teenagers burst into the shop and attacked a worker.
Former security worker Ross, 28, was caught up in the terrifying incident with his wife, who filmed it.
Aldi staff eventually managed to force the youths from the store by shoving them and whipping them with belts. But seconds later, they returned and tried to force their way back in by smashing the glass doors with a fire extinguisher.
'They were like animals'
Builder Ross said: "They were just kids, aged between 13 and 15 at most, I reckon. They were all wearing school uniform under hoodies and tracksuit bottoms.
"A few had their hoods up, but all were happy to be seen. They were like animals."
Ross thinks it was a planned attack because the boys went straight for an Eastern European worker.
"It looked like he was expecting the attack because the boys picked him out and he defended himself quickly."
After breaking back in, Ross said one boy smashed a fire extinguisher into the bridge of a worker's nose. He added: "I gave first aid to that man. His nose was clearly broken.
"Another was punched leaving him with a broken cheekbone. It was distressing to see. There was glass and blood everywhere. The children and customers should not have been made to go through that."
Ross was particularly shocked by how long it took police to respond. His wife alerted police to the "gang break in" at 6pm on Monday, but the police took 20 minutes to arrive.
'It shouldn't take that long for police to respond'
"They apologised for being late when they arrived saying they had only just got the call," Ross said.
"It shouldn't take that long for police to respond to a major incident in a supermarket. There were kids and shoppers trapped inside."
A Met Police spokesperson said: "Police were called on Monday, 30 September at approximately 18:00 hours to reports of a disturbance and assault in Victoria Retail Park, Ruislip. There were reports of a group of youths assaulted members of staff at a supermarket, threw items and damaged property. Officers attended but all suspects had left the scene."
Police added there were no reports of serious injuries. Enquiries continue to identify and trace those involved.
An Aldi spokesperson said they would not comment on an ongoing police investigation.