July 19, 2003 -- Detectives have pieced together the final tragic moments of an NYPD lieutenant and his longtime girlfriend who were found shot to death in their bed, The Post has learned.
Armed with new evidence from the medical examiner, investigators have reconstructed how Lt. Stephen Bouillon initially planned to fatally poison himself and his paramour, Joan McHugh, with carbon monoxide while they slept in their Roslyn Heights, L.I., home.
But instead, he awoke and used a gun to execute her and then himself.
The two - who by all appearances shared an idyllic life - were found lying along side each other. She was on her left side with a wound to the back of her head while Bouillon was discovered lying face down with a frontal head wound.
Sources say before they went to sleep last Sunday evening, Bouillon went outdoors and ran a pool hose from his BMW in the garage to the central air conditioning unit, hoping to fill the house with enough carbon monoxide to kill both him and his paramour of more than 20 years while they slept.
A preliminary test on their bodies has shown traces of carbon monoxide in their blood, but not enough to kill them.
Authorities believe that when Bouillon awoke in the middle of the night and realized his initial plan was not working, he reached for his weapon, shot McHugh, 47, while she was asleep and then turned his gun on himself.
When the usually punctual Bouillon, 49, failed to show up at his Internal Affairs Bureau office at 9 a.m., his supervisors drove out to check up on him.
They heard the muffled sound of the running auto and saw the pool hose running out of the garage door.
Nassau County cops entered, setting off a motion detector on the house alarm before making the grim discovery.
The motive remains a mystery.
The pair had just returned from a Florida vacation, had celebrated Bouillon's upcoming 50th birthday and were making plans to build a pool. The home was owned by McHugh, a former nurse who became a partner at a Manhattan health care consulting firm.
Authorities are checking their phone records and e-mails and talking to doctors to see if a health crisis may have sparked the carnage.