Louis Tomlinson fans were forced to seek shelter from golf ball sized hailstones at his gig last night (21).

The hailstorm hit the Red Rocks Park and Amphitheatre in Morrison, Colorado.

A video shows hundreds of fans squashed into a shelter next to the amphitheatre where the former One Direction man was performing.

The event was officially postponed.

Eric Brinkman, 47, from Atlanta, Georgia, who captured the video, was visiting Denver and attending the concert for his daughter's 16th birthday.

Eric, a self-employed graphic designer, said: "There were dark clouds and lightning - but no rain - all around for an hour before the hail started."

"The first opening act made it on stage at 7pm, but the concert postponed the second opening act at 8pm and told everyone to go to their cars."

"They later gave an all clear about one hour before the hail hit and Louis was scheduled to be on stage about 9pm."

"It's no wonder that so many people were caught outside."

"I saw the second storm approaching on my phone radar app, so my family was able to seek shelter before the chaos."

"So many people got stuck without any options of shelter, and were just getting blasted by golf and tennis ball size hail."

"It's terrifying to think of being helpless and running for cover when there was none."