"I had to leave David behind in order to save my own life," says Tiffany Hartley.
"It was the hardest, the worst, decision anybody ever would have to make and I had to leave. I knew I had to leave," Tiffany told INSIDE EDITION.
The Hartleys were riding jet skis on Falcon Lake, which straddles the Texas-Mexico border, and exploring a half-submerged mission chapel.
David was shot in the head and his body was never recovered. Tiffany managed to escape and she called 911.
911 Operator: "Are you sure that your husband got shot?"
Tiffany Hartley: "Yes! In his head! He was thrown off the jet ski and I couldn't pick him up to get him on mine."
"What do you say to people who to this day question your story?" INSIDE EDITION's Paul Boyd asked Tiffany.
"If they don't want to believe what happened, that's their choice. If they want to judge me, that's their choice. Ultimately I don't care," she said.
Tiffany and David were high school sweethearts and married when Tiffany was just 20 years old.
On her first Thanksgiving weekend without him, Tiffany is struggling to start a new life. Paul Boyd visited her in Colorado, where the couple's love first blossomed.
"Everywhere I go, every street I go on, there's some memory of the two of us," Tiffany said.
She clings to Tori, the dog they both loved.
Tiffany never imagined having to go through life without David, but she says he inspires her to move on.
She said, "He would say, 'Live the life as if I was here. Go travelling, go and do the things you've always wanted to do.' "
Tiffany has started a campaign fighting for stricter border security in her husband's name.