Junior Seau, the 43-year old former NFL linebacker who shot himself in the chest in May, apparently only had traces of a sleep aid in his system when he died.

Autopsy reports show Seau had nothing stronger in his system than the sleep aid–Zolpidem–and faint traces of Naproxen, a common over the counter drug used to help ease arthritis. His death has now officially been ruled a suicide.

“No alcohol, common drugs of abuse or medication were detected,” read the report. “Based on the autopsy findings and the circumstances surrounding the death as currently understood, the cause of death is perforating gunshot of chest and the manner of death is suicide.”

Officials weren’t immediately sure what to make of Seau’s death when the investigation began, as a self-inflicted gunshot wound to the chest is a rare form of suicide. His family said they suspected nothing was amiss when talking to him in the days and hours leading up to his death, and Seau’s mother seemed to think an outside party had been involved, telling responding officers she didn’t “understand who would do this” to her son.

Seau left no note explaining his actions. His family has donated parts of his brain to scientific research.