As search efforts entered their fifth day in the devastating Central Texas floods, Gov. Greg Abbott vowed to find "every single missing person," stressing that the mission will not end until all victims are accounted for amid a death toll that has surpassed 100.

The risk of the catastrophic flooding that struck Texas Hill Country as people slept on July 4 and left at least 120 dead was potentially underestimated by federal authorities, according to an ABC News analysis of Federal Emergency Management Agency data, satellite imagery and risk modeling.

Texas Gov. Greg Abbott on Wednesday ordered state legislators to convene a special session on Monday as the death toll rose to at least 120 people and 172 reported missing in Fourth of July flooding in the Hill Country.