Gordon Rowe, 61, was found slumped in a car on a road known as Devil's Highway. A post-mortem examination revealed that he died of carbon monoxide poisoning.
A 19-month investigation into allegations of sexual and physical abuse at his Longcare homes at Stoke Green House and Stoke Place Mansion House, Stoke Poges, Buckinghamshire, was about to conclude. A police source said Mr Rowe would have been charged.
The East Berkshire coroner, Robert Wilson, who heard that he left a seven-page letter to his two sons and second wife, recorded a verdict of suicide.