The grieving grandmother of South Carolina girl Faye Marie Swetlik released a heartbreaking video of the 6-year-old singing “You Are My Sunshine” — as cops launched a homicide investigation into her death.

Ruth Collins posted the short, touching clip to Facebook shortly before police announced that Faye — who vanished after getting off a school bus three days earlier — was found dead on Thursday, FOX Carolina reported.

Collins said that she and Faye would sing the song together every day.

Faye’s body was discovered in the Churchill Heights neighborhood where she lived, the Lexington County Coroner’s Office said.

Investigators also noted Thursday that they’d found the body of a man in the same neighborhood during the investigation, but didn’t offer any details to connect the two deaths.

A homicide investigation into the girl’s death has been launched, Cayce Department of Public Safety Director Byron Snellgrove told reporters during a Thursday news conference.

The first-grader disappeared on Monday after getting off a school bus in her neighborhood. Relatives last saw her playing in a yard before reporting her missing to police at about 5 p.m. Monday.

No suspects have been identified in the girl’s death, Snellgrove said.

“We would like to remind you that our investigators are processing a large amount of physical evidence,” the Cayce Department of Public Safety posted to Facebook Thursday evening. “This is a highly methodical process, so please bear with us as we will continue to communicate with you as much as possible and in the same manner for which you have become accustomed. As we weep, we work.”

Collins changed her Facebook profile photo to a single burning candle after authorities announced the news.