Two 18-month-old twins died in Arizona after an attacking bee prompted a mother to let go of the children’s stroller and it rolled into a swiftly moving canal.

Police said Alexis Keslar was walking with her twin sons, Silas and Eli Keslar, along a canal in Yuma on Friday when the freak accident occurred, according to CNN.

“The stroller rolled away from her into the canal, with the boys belted in the seat,” police said Monday, according to CNN.

Keslar attempted to rescue the toddlers, authorities said, but was unable to reach them because of the waterway’s swift current and steep walls, CNN reported. After struggling to exit the canal, Keslar went to find help.

Rescuers located the twins more than an hour later and transported them to a local hospital, where they were pronounced dead, according to the New York Daily News.

“No parent should ever have to lose a child, you know, let alone both of them at the same time,” family friend Marlene Gleim told NBC affiliate KYMA. “That’s what really, really is heartbreaking to me, because those little boys were, you know, meant so much to so many people.”

Yuma police said canals — popular destinations for joggers and bicyclists — often appear smooth, leading people to underestimate their depth and current, according to the Yuma Sun. People who enter canals, police noted, also underestimate how difficult it is to “climb back up many of the canal embankments,” the Sun reported.

A GoFundMe page started by a Yuma woman to help the Keslar family pay for medical costs and funeral expenses has raised more than $22,000.