Once there, Mr. Muñoz and his family said they wanted to apply for asylum, The Post reported; Border Patrol agents then told them they would be separated.

Image Marco Antonio Muñoz Credit... Starr County Sheriff’s Office

While at the processing center, the Customs and Border Protection spokesman said, Mr. Muñoz “became disruptive and combative,” so the authorities moved him to a jail in Starr County, Tex. — about 40 miles west of the processing center — for an overnight stay.

Although the statement did not say whether Mr. Muñoz was with family members at the border, or explain why he became combative, media outlets reported that he grew upset after learning that his family would be split up.

A public report posted by the Texas attorney general says Mr. Muñoz, 39, was booked into the jail the night of May 12. He was “combative and noncompliant” and scuffled with a detention officer, the report said, before being placed in a padded cell late that night.

Throughout the evening, officers checked on Mr. Muñoz every 30 minutes, the report said, but during the morning shift, different officers found Mr. Muñoz dead on the floor.