A man in custody at the Harlingen city jail was found dead in his cell hours after his arrest, police said Friday.

Frank Cantu Rivera, 44, was arrested Thursday morning for an outstanding aggravated assault with deadly weapon warrant, according to a news release from the Harlingen Police Department.

Police say Rivera was initially transported to a local hospital for medical evaluation, but he refused.

After Rivera was booked into the jail, he was placed into a cell awaiting arraignment, according to the release.

“At approximately 2:45 p.m., a Harlingen City Jailer found Rivera unresponsive in the cell,” the release said, adding that jail personnel immediately started first aid and medical personnel were called to the jail section.

“Several attempts were made to revive Rivera, but he was pronounced dead,” the release stated.

This case is currently under investigation by the Texas Rangers.