(ABC News) A 3-year-old boy has died after he was found locked in a hot car in Sweetwater, Tennessee, on Monday, authorities said.

The boy’s grandmother — who is also his guardian — told authorities she had been mowing a neighbor’s lawn while a teenager was watching several children at the home, according to the Monroe County Sheriff’s Office.

When the grandmother came back to the home, they realized the boy was missing, officials said.