RUSTON (AP) — Louisiana Tech University’s mascot, Tech XX, has died.

The 4-year-old English bulldog and face of the university was reported missing Sunday from the Ruston animal clinic where he’d been staying. Authorities initially said the animal had been let out for a bathroom break and when a worker went to bring him back inside, Tech XX was nowhere to be found.

On Wednesday, Dr. Patrick Sexton, the clinic’s owner, reported the dog had died of heat stroke on Sunday.

“Regretfully, I learned this morning that through negligence of an employee, Tech XX was left outside too long on Sunday evening and passed away from a heat stroke,” Sexton said in a statement released by the university. “That employee unfortunately chose to handle it the wrong way and attempted to cover it up. Due to this negligence, the employee is no longer employed by Sexton Animal Health Center.”

Tech XX was named mascot in 2008, replacing Tech XIX, who retired due to health concerns.

Sexton said he, his family and staff were “extremely upset at this tragic turn of events.”

“Tech XX was a member of our immediate family and a daily part of our lives for the past four years. We are devastated over the circumstances of his passing, and there will be a large void in our hearts for some time to come,” he said.

The university, in a statement, said it was saddened to learn of Tech XX’s death. “He will be remembered for being a fan favorite and a symbol of the spirit of Louisiana Tech.”