That's the contention of the comedian's widow, Rhonda McCullough, who has filed a wrongful death lawsuit in Chicago against one of his doctors.
Mac, who for years suffered from sarcoidosis, a chronic autoimmune disease, died on Aug. 9, 2008, at age 50, of heart failure during a bout of pneumonia.
McCullough says in her suit that Dr. Rene M. Earles, a dermatologist who regularly treated Mac for the skin lesions caused by his sarcoidosis, was negligent by failing to recognize signs of medical distress or get emergency attention when Mac came to his Chicago office on July 17, 2008, three weeks before his death.
Mac arrived at Earles's office with a fever, fatigue and trouble breathing. During the nine hours Mac spent there, he had unstable vital signs, and both rapid heart rate and breathing, but Earles didn't "recognize cardiopulmonary instability" or "abnormal vital signs and signs of impending respiratory failure" and failed to either call 911 or get the actor to an emergency room, according to the lawsuit.
As a result, Mac died unnecessarily, the suit claims, and his family "has been deprived of [his] love, companionship, and emotional support."
One physician wrote in an affidavit supporting the lawsuit that if Earles had dialed 911, Mac would have received timely medical care and "would have survived."
Earles did not respond to a request for comment from PEOPLE, but told the Chicago Sun-Times that he's devastated by the death of his longtime patient and friend. He told the paper he gave Mac oxygen and let him rest for about four hours after he arrived at his clinic around 2:30 p.m.
Believing that Mac was suffering from a reaction to a drug given to him by a different physician for a cold, Earles gave the actor medication to stop the reaction and phoned Mac's doctor, who said the star had pneumonia in both lungs and should be admitted to the hospital.
Earles said Mac left the clinic and was taken by his driver to the hospital at about 10 p.m. Earles believed he treated Mac properly, and that Mac ended up contracting a different strain of pneumonia while in the hospital, the Sun-Times reports.
The actor's death "was entirely devastating," Earles told the paper. "Look, Bernie was my patient. Bernie was my friend. We became extremely close – we were like brothers."
McCullough is seeking at least $50,000 in damages.