Monjack's mother-in-law, Sharon Murphy, found him unconscious in the Hollywood Hills home he once shared with his late wife on Sunday (23May10). Paramedics determined he had suffered a cardiac arrest and pronounced him dead at the scene.
Monjack's representative, Roger Neal, revealed the overweight Brit was in need of heart bypass surgery when he died.
Officials have since concluded there were "no signs of foul play or any criminal activity involved" in Monjack's death, although the cause won't be known until results from toxicology tests are returned.
But the actress' sibling, Tony Bertolotti, admits he suspected something was wrong in the Monjack/Murphy household prior to his death, although he refuses to go into further details.
He tells the National Enquirer, "I wasn't shocked to be honest. The guy was insane."
Clueless star Murphy, Sharon's daughter with Angelo Bertolotti, died at the same Hollywood property in December (09).
Monjack will be buried beside the tragic actress at Forest Lawn Memorial Park in Los Angeles on Thursday (27May10).