The body of Albert Foulcher, 49, was found underneath a bed
when police burst into the fourth-floor apartment in the
southern town of Beziers.
Foulcher fired through the door of the flat when he realised he was surrounded and then apparently shot himself, police said.
Police launched a manhunt last week after Foulcher, in Narbonne, shot dead two policemen and two witnesses who had testified against him at his trial for the murder of a fellow insurance agent.
Gunned down
Foulcher was not present at his trial, was arrested in June 1993, six months after the killing.
But he was freed on bail in October 1996 after an appeals court ruled that his long pre-trial detention violated the European Convention of Human Rights and soon stopped reporting to the authorities.
The two policemen who died last week were gunned down after Foulcher's former colleague, Pascal Herrero, called for help, after realising the convicted murdered had tracked him down.
Mr Herrero had testified against Foulcher at his trial, and understood that the killer was seeking revenge.
Tracker dogs
But the two officers were themselves killed before Foulcher turned the gun on Mr Herrero.
Foulcher then drove to the office of another former associate, Maurice Michaud, who had also testified against him. He too was shot dead.
Up to 500 officers - some using tracker dogs - joined the huge manhunt.
Police provided bodyguards for two more people connected with the murder trial as the search went on.