The emergency management coordinator of Kerr County, which bore the brunt of the deadly July 4 floods in the Texas Hill Country, testified on Thursday that he was sick and asleep when the floodwaters rose in the middle of the night, eventually killing 108 people in the county.

The admission by the official, William B. Thomas IV, came at the start of an extraordinary hearing held by state lawmakers in a packed convention center in city of Kerrville, a short walk from the banks of the Guadalupe River, which surged to record levels in the predawn darkness of July 4.

Hundreds of residents attended the hearing, and many of them hoped to testify in what was expected to be an emotional session lasting for more than 12 hours.

The hearing began with statements from county officials, including Mr. Thomas, the county’s emergency management coordinator since 2015. Mr. Thomas had not spoken publicly since the flood, as questions were raised about his whereabouts and why neither he nor anyone else in the county had issued more warnings about the rapidly worsening situation along the river.

“I want to directly address questions about my whereabouts,” Mr. Thomas said. He explained that he had always planned to be off work on July 3 “to fulfill a commitment to my elderly father,” and that because of a “progressing illness,” he had stayed home.

“I stayed in bed throughout July 3 and did not participate in the regularly scheduled 10 a.m. and 3 p.m. Texas Emergency Management Coordination Center coordination calls,” he said.