A medical condition Monday afternoon may have caused a 44-year-old city bus driver to crash through a 170-year-old wall at historic Kawaiaha’o Church, seriously injuring himself in the accident.

“We suspect that there was a medical issue of some kind,” Oahu Transit Services President Roger Morton said Tuesday. “We’re not sure what kind of medical issue it was. There’ll be further evaluations by medical people over the next days and weeks.”

The driver, who hasn’t been identified, remains hospitalized in a lot of pain, suffering from a knee injury, Morton said. 

Morton said he couldn’t recall in his 30-plus years with Oahu Transit Services ever having such an accident.