A man who witnessed Monday’s mass shooting at a supermarket in Boulder, Colorado, in which 10 people were killed has recalled the terrifying moment he first heard gunshots and realised he had to run for his life.

In interviews on CNN, Ryan Borowski remembered seeing a look of horror and fear on another customer’s face and then fleeing with staff and other shoppers through the maze-like rear of the King Soopers grocery store.

Store workers helped customers avoid dead ends and between one and two dozen people fled through the store’s loading dock, said Borowski.

He’d only gone into the store to buy ice cream, soda and chips.

“Absolutely insane,” Borowski told “CNN Tonight” anchor Don Lemon of the chaos, for which a suspect has been arrested.

“It was just ‘go go go, get out of here,’” he added.

“Boulder feels like a bubble and the bubble burst and that’s heartbreaking. To think that people died today,” Borowski told “Outfront” anchor Erin Burnett.

“It doesn’t feel like there’s anywhere safe anymore, sometimes,” he continued.

“This feels like the safest spot in America and I just nearly got killed for getting a soda, you know, and a bag of chips. Doesn’t feel good.”