Lafayette resident Heidi Nunes-Tucker said Tuesday that a photo or video posted on social media shortly after the attack shows the waiter trying to help her gravely injured husband, 42-year-old Jared Tucker.
VIDEO: Family: Bay Area man is victim of Barcelona attack
She doesn't have a copy of the post, but says she and her family want to find and thank the waiter.
She says anyone who stopped to help amid the chaos "is a testament to the helpfulness and love" that strangers can show for each other.
PHOTOS: Images from scene of struck pedestrians in Barcelona
Nunes-Tucker is in Barcelona as her husband's body is being prepared for her to take home.
A GoFundMe page has been created for the family of the victim. Click here if you'd like to help.
ABC7 News contributed to this story.