The grieving grandmother of one of four children killed in a house fire last week collapsed in a church pew as the children's funeral was about to begin, and was later pronounced dead of a heart attack.

Verna Glenn, 58, slumped into the arms of family members as she sat looking at the small white casket holding her 6-year-old granddaughter, Marlese Glenn.

Fire officials said she died of a heart attack.

"It's the kind of thing that is unimaginable, to be with this family in the worst possible time of their loss and then to have it compounded with the loss of a grandmother on the very same day," said the Rev. Alan Ragland, pastor of the South Side church where the funeral was held.

Marlese, her 2-year-old sister LeShawn Harris, and their cousins Dontrell Harvest, 8, and Tykia Harvest, 9, died in the March 29 fire. Two adults were also injured in the blaze, which fire officials have said may have been caused by an electrical malfunction.