Brie Larson had the best reaction to getting caught in the middle of a fan's proposal

Brie Larson attends ACE Comic Con Midwest at Donald E. Stephens Convention Center on October 12, 2019 in Rosemont, Illinois. (Photo by Daniel Boczarski/Getty Images)

Brie Larson got a big surprise when she found herself in the middle of a proposal at ACE Comic Con in Chicago over the weekend and had a priceless reaction to being part of the big occasion.

The Captain Marvel actor was posing for pictures with two fans at a meet and greet when one of them, John Chambrone, got down on one knee to pop the question to his partner, Richard Owens.

The amusing moment was captured on camera, with one photo showing a shocked Larson looking toward the camera as Chambrone grins with his arm round her waist while a visibly stunned Owens holds his hands to his mouth.

Read more: Scarlett Johansson is 'pushing' for the all-female Marvel movie

Larson looks between the happy pair in subsequent images before the final shot shows her peeping out from behind the kissing couple, still wide-eyed.

She expressed her delight at being witness to the momentous event on Twitter.

"Y’all I was present for a proposal and I am CHANGED. Much love to the happy couple!!!!" Larson exclaimed as she shared the photos of the moment posted by another fan.

Chambrone later shared his excitement at the encounter in a post to Facebook as he described it as "the most epic moment of my life".

US actress Brie Larson arrives for the World premiere of Marvel Studios' "Avengers: Endgame" at the Los Angeles Convention Center on April 22, 2019 in Los Angeles. (Photo by VALERIE MACON / AFP / Getty Images)

Meanwhile, last week saw Larson reveal that the female members of the Marvel Cinematic Universe approached studio boss Kevin Feige to make an all-female superhero movie.

She explained it was something they "are really passionate about" and that it “maybe” could happen if the demand from fans was there.