Armed police descended on a suspected gunman inside a busy Lidl supermarket while horrified shoppers were told to "get down".
Police were summoned to initial reports of firearms inside the London shop on Ealing Road, Harrow in the north west at around 2pm on Tuesday.
Videos shared online have captured four armed police officers wrestling a man, scrambling on the shop floor.
Horrified shoppers were left in disbelief at the scene as they were ordered to "get down" repeatedly.
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Nevertheless, the panic from the sudden ordeal fuelled hysteria with customers, many of whom ran through the aisles.
One voice in the background could be heard saying "no way" while the shocking ordeal unfolded.
Police have since confirmed officials have arrested a man on suspicion of possession of a firearm and possessing a firearm with intent to endanger life.
A spokesman said: "We understand this has caused concern for those in the local community and we will have an increased police presence in the area."
Footage showed police wrestling a man on the ground
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No shots were fired, nor were any injuries reported, they added.
London has witnessed an ever-growing surge in shoplifting.
But, on Tuesday, the Metropolitan Police said they were solving 50 per cent more shoplifting cases in locations where they were trialling new technology to identify suspects more quickly.
The areas using the new technology, which was introduced in January, have included Lewisham, as well as more areas across the capital.
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While the force's positive outcome rate is 14 per cent on average, the areas which have hosted the new rollout has seen their positive outcome rate rise to 21.4 per cent.
The Metropolitan's deputy commissioner Matt Jukes said: "Cracking down on shoplifting is a clear priority for the Met.
"By strengthening neighbourhood teams, using better intelligence and focusing on hotspot locations, we are arresting repeat offenders who cause the most harm to retail staff and local businesses.
"We’re also using new technology to work faster and more effectively, giving officers a much clearer picture of offending and helping build stronger cases.
"Where we have trialled this retail crime technology, more than one in five shoplifting cases are being solved.
"Strong partnership with retailers is essential. When crimes are reported promptly and CCTV is shared quickly, officers can take decisive action."
On Tuesday, the Metropolitan Police celebrated a victory over its use of Live Facial Recognition after it was challenged by privacy campaigners in court.
Commissioner Sir Mark Rowley hailed the win as an "important victory for public safety".