A service is being held in Maine for a 50-year-old secret service agent who died while training at the Bush family compound at Walker’s Point in Kennebunkport.

Keith Mills, a Secret Service officer who protected the late President George H.W. Bush and former President George W. Bush, died Sunday.

An autopsy has been conducted, but the cause of death was not released.

Mills’ death is considered a line-of-duty death.

In a statement, former President George W. Bush said he and his wife Laura “were saddened by the sudden loss of Keith Mills.”

Bush called Mills a “dedicated public servant and exemplary member of the United States Secret Service.”