Lindsay then died of the cancer hours after she and Mosher were Wednesday at St. Francis Hospital in Hartford, Connecticut.
"It reminds me of someone who is crossing the finish line of a marathon or something", Mosher told WFSB.
Lindsay told Karas she was afraid she wouldn't make it until her wedding day, and when her turn took a turn for the worse, her family, friends and doctors moved quickly.
"She's getting to shout from the rooftops that she loves Dave and is able to say 'I'm his wife, '" Karas said. "The way we would talk about it, you alway kind felt this isn't it". On 23 December 2016, Heather was diagnosed with terminal breast cancer. He went ahead with the proposal.
As Heather's cancer spread their wedding plans did not falter, and they remained committed to tying the knot.
"We found out it was in her brain and a couple months later, she was on life support with a breathing tube", David said.
Heather and David Mosher got engaged exactly a year before she passed away. "That morning, we had a doctor's appointment after finding a lump on her chest", he says. "I proposed to her", Mosher told InsideEdition. The vows were hard for Karas to document, but the bridesmaid took her camera out towards the end, just in time to capture Heather's fleeting joy, according to WFSB. "She held on to stay alive for the wedding. a wedding to the man of her dreams".
Despite many experts saying she would not make it through October, Lindsay kept going. But since Heather's condition worsened, it was moved up to 22 December, just before Christmas.More news: Philippe Coutinho: Liverpool boss Jurgen Klopp bracing himself for £130m Barcelona bid
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The wedding had been brought forward and had originally been planned for Dec 30, which, in another twist of bitter irony, ended up being the date of her funeral.
The heartbreaking scene was captured in photos by one of the bride's best friends, Christina Karas, who also served as a bridesmaid.
Heather valiantly proclaimed her vows to David.
Part of her last words were here wedding vows. Under a street light, David dropped to a knee and popped the question.
"We had a great love", Mosher said.
The couple had originally planned their wedding for December 30, 2017, but the bride-to-be's condition necessitated speeding up the timetable.
He added: 'Heather said, "I want to keep fighting", so that's the mantra I'm picking up.
In the end, however, they were able to help Lindsay into her gown and then into the chapel where she met Mosher to exchange vows. "She wanted me to be in a dress, and I just had to get into wedding mode because my heart was in "losing my best friend" mode". Instead of preparing for a wedding at Plantsville Congregational Church, David Mosher will be attending his wife's funeral at the church, at the same time they were set to be married.