Michael Jackson's doctor told police he left the singer for about two minutes after giving him the anesthetic propofol for sleep and returned to find Mr. Jackson no longer breathing.
In a dramatic audio recording of Conrad Murray's police interview two days after Mr. Jackson's June 25, 2009 death, the physician also said that the singer had begged him for hours to help him sleep that night.
The two-hour tape was played publicly in its entirety for the first time on Friday at Dr. Murray's trial on manslaughter charges. Authorities have determined that Mr. Jackson died of an overdose of propofol combined with sedatives.
Dr. Murray said that he gave Mr. Jackson propofol at around 10:50 a.m. on June 25, after trying unsuccessfully to get him to sleep with sedatives all night.
"I watched him for a long enough period that I felt comfortable, then I needed to go to the bathroom so I got up and went to the bathroom," Dr. Murray told detectives.
"Then I came back to his bedside and was stunned in the sense that he wasn't breathing," Dr. Murray added.
Dr. Murray's account to police however differed from evidence presented by prosecutors at the two-week old trial.
They have presented phone records showing that Dr. Murray made and received a series of cellphone calls between 11:07 a.m. and shortly before noon, when he is believed by prosecutors to have discovered that Mr. Jackson was no longer breathing.
Until now, Dr. Murray has been a silent figure in the trial, writing notes and whispering to his team of attorneys as the prosecution details its case against him.
The physician's lawyers say Mr. Jackson caused his own death by giving himself another dose without Dr. Murray's knowledge.
Dr. Murray told police that he gave Mr. Jackson propofol frequently for a month before his death, saying the singer wanted to sleep for 15-18 hours a day. But Dr. Murray said on the tape he was trying to wean Mr. Jackson off what the pop star called his "milk."
Dr. Murray was hired to care for Mr. Jackson as he prepared for a series of London comeback concerts. He faces up to four years in prison if convicted.
In the first two weeks of the trial, prosecutors have portrayed Dr. Murray as a man who ordered vast quantities of prescription drugs for Mr. Jackson but who failed to monitor the singer properly, and then tried to hide some of the drugs before calling an ambulance.