A mob of masked thieves rampaged through a jewellery shop with pickaxes and held the guard hostage as they stole £1.2million worth of jewellery, police said.

The US Department of Justice has just released CCTV footage of the chaotic scene, which occurred in June last year. Suspects can be seen running riot as they smashed the glass counters with their weapons and nearly cleared the Californian store of its assets within 70 seconds. Authorities said a fleet of cars pulled up outside Kumar Jewelers in Fremont before nearly a dozen people descended on the shop, in what they described as a “mob style takeover”.

In what appeared to be a coordinated approach, some masked suspects can be seen smashing the counters with hammers and pickaxes, while others jumped over the counters and grabbed necklaces hanging up on the wall in their gloved hands.

Some of their arms were completely stuffed with entire display racks as they sprinted out of the store and into multiple getaway vehicles. Two gunmen held the security guard hostage during the heist until the last person had left the shop.

In total, around £1.28m of merchandise was stolen in the raid, which was more than three-quarter’s of Kumar Jewlers’ entire stock. Since they fled in multiple cars, officers were left with no choice but to pursue only one vehicle.

In court filings obtained by the East Bay Times, federal prosecutors wrote: “Forced to decide which car to pursue, officers continued after [a] black Acura, which led them on a pursuit through several residential areas in Fremont.

“During the pursuit, the black Acura passed other vehicles on the wrong side of the road, ran stop signs at multiple intersections and reached speeds of approximately 80 miles per hour while veering across lanes.”

After a car crash and a pursuit on foot, police arrested four men aged between 19 and 20. Authorities have not detained any other suspects.

Prosecutors believed that the masked robbery may have been linked with another theft three months later in the same state, at a San Ramon store. Around £1.28million worth of jewellery was stolen in that heist.