It was clear long before Michael Jackson ever arrived at the hospital yesterday that his condition was critical.

In a newly released audio tape (which can be heard here), an unidentified caller tells a 911 operator that they have a 50-year-old “gentlemen” who is not conscious or breathing. The male later explained that a personal doctor had been with the patient and was already working on trying to revive him. “He’s pumping his chest but he’s not responding to anything,” the caller says.

That physician - since identified as Dr. Conrad Murray - is wanted for questioning by the Los Angeles Police Department. Although officials did speak to Murray yesterday, they have been unable to reach him for further comment today.

Despite a quick response from paramedics, Michael Jackson was later pronounced dead at 2:26 p.m. at Ronald Reagan UCLA Medical Center.

An initial autopsy on the singer did not conclusively determine a cause of death. More won’t be known until toxicology results return in approximately 6-8 weeks.