Trevor Marquis Rowe, 27, is alleged to have left her on the floorboard of his passenger seat while he went to work.
According to the arrest warrant, he stuffed the tot into the bag and came back to check on her at around 1pm.
He said that when he checked on her, she was crying lightly but she was still breathing.
The documents claim Rowe then drove to a fast food restaurant, before putting the backpack containing Marion in the boot of his car and returning to work.
When he next checked on the little girl just before 5pm, he discovered she had stopped breathing.
He drove to another street before calling the emergency services and starting CPR, reports the Abilene Reporter News.
The child was rushed to University Medical Centre where she was pronounced dead.
When questioned by police, Rowe allegedly admitted knowing it was dangerous to leave a child in a car.
He is also said to have told police the child had not eaten since 8pm the night before.
Rowe was charged with capital murder and held on a $2million bond.
