Heavy D The FRANTIC 911 Call 'He Is Not Breathing!'

12/28/2011 2:00 AM PST

Life and death were separated by a matter of seconds for Heavy D, who stopped breathing while a bystander was on the phone with the dispatcher -- and you hear it all unfold in the frantic 911 recording obtained by TMZ.

One of the first questions the dispatcher asks ... is D breathing? The caller -- who's so freaked out she can't stop screaming -- says he is.

Moments later, everything unravels ... as the caller shouts that the rapper has stopped breathing, and people on the scene then scramble to perform CPR.

An ambulance arrived shortly thereafter ... but it was too late. Heavy D was pronounced dead at the hospital an hour later.