The man, identified as Walt Daniels, fell about 25 to 30 feet out of a booth that was to be used by Broncos assistant coaches and landed on the loge level. He was administered CPR before being taken to Sharp Memorial Hospital.
Workers later cleaned up a puddle of blood.
The accident delayed the opening of the gates by about 40 minutes.
The Chargers released a statement saying they will provide more information as it become available.
The Associated Press contributed to this report.