Mr Hartman, 49, who first achieved national fame through his impersonations of Ronald Reagan and Jimmy Carter on Saturday Night Live, was found dead his home in the Encino neighbourhood of Los Angeles early yesterday morning after Los Angeles police entered the home in response to an emergency 911 telephone call.
It was while the officers were in the house and evacuating two young children, believed to be the Hartmans', that a second gunshot was heard in a bedroom. It is believed that shot was fired by Mrs Hartman.
The Los Angeles police department said an investigation was only just under way. It was widely assumed, however, that Mrs Hartman was responsible for killing her husband some hours before the arrival of the officers and had then taken her own life.
"We are investigating this as a possible murder," Lieutenant Anthony Alba said. "We know for sure that the female inflicted her own gunshot wound. She shot herself as police were removing the second child from the home. Mr Hartman had been dead for a while."
Newscasts were last night airing footage of police officers carrying a young girl, with tousled blond hair and still in her night clothes, out of the house and down the street to an awaiting ambulance. The Hartmans had two children, a boy aged nine and a girl who is six.
Though not widely known outside of the United States, Mr Hartman, had progressed to becoming one of American television's most popular comedy stars. Since 1995, he has starred as the vain and self-obsessed Bill McNeill in a weekly NBC sitcom called News Radio.
Despite recent clashes between Mr Hartman, and network executives over its scheduling in prime-time, News Radio has consistently ranked as one of NBC's most successful sitcoms and was recently renewed for a new season by the network. Other NBC hits include Friends and Frazier.
There were no clues last night as to what might have happened between Mr Hartman and his wife to have brought on such violence.
Money was surely not a problem. Mr Hartman recently boasted that he had made more money through commercials and endorsements than from the whole run of News Radio.
A neighbour and friend of Mrs Hartman, Sue Kaplow, said she had had no indications of domestic tension. "She left a really happy message yesterday. Everything was fine. We left each other little messages all of the time."
It is not the first time that tragedy has marked veterans of Saturday Night Live. In 1982, John Belushi was found dead aged just 33 after a drugs overdose. And just last month Chris Farley, also an SNL alumnus, also died at 33 from drugs abuse. Like Mr Farley, Mr Hartman was Canadian- born but grew up in the United States where he based his career.