No one knows why Shannon Elizabeth Steinbach did the unthinkable. Police in Schleswig, Iowa say the mother of two killed her infant child and then killed herself.

We talked to Shannon's grandmother, Cleone O'Neill, and the 86-year-old had a simple message: her granddaughter was a good person and a good mother.

Shannon's youngest child, Hope, was little more than a handful at birth, born premature, but loved from the first moment -- love that helped her grow and until she was ready to go home.

Grandmother says the baby's mother, Shannon, was a good mom.

Cleone says, "She was a good girl. I helped raise her. I took care of her some when she was growing up. She was a quiet little girl; very sensitive. That's the way she was raised -- to love people and care for people."

But something happened. Somewhere along the line, Shannon stepped outside of herself. No one is sure what happened but the possibility of postpartum depression has surfaced.

Dr. Sonja Kinney is with the Nebraska Medical Center and she spoke in general terms about postpartum depression.

She said it can involve, "a lot of people second guessing themselves; putting a lot of pressure on themselves; needing to be the perfect mom; the perfect wife; having the perfect baby.

"The most extreme postpartum depression is people who have postpartum psychosis. They may have different messages coming in, telling them some things are happening and they need to do something to themselves or the baby."

On May 19, the Crawford County, Iowa sheriff's department responded to a 911 call in Schleswig. Authorities found the bodies of Shannon and Hope.

The case has tentatively been ruled a murder-suicide. Authorities say it appears that Shannon hanged herself in the basement of the family home. Four-month-old Hope was found in an upstairs bathtub in approximately five to six inches of water.