Since Dr. Murray was in a sticky position as the physician of Michael Jackson, inappropriately using anesthetics and everything, I can see why he would want to hide the evidence. But he probably should have waited until Michael Jackson stopped dying.
According to a witness at the scene, while Michael Jackson was busy dying in his bed, his doctor stopped CPR and then delayed calling 911 so that he could collect drug vials to hide them.
Alberto Alvarez, Jackson's logistics director, ran to Jackson's room after he heard a call for help to find Dr. Murray performing CPR with one hand on Michael Jackson. After coming into the room, Alvarez was supposedly told by Dr. Murray to collect some vials and put them in bags.
Alvarez, while Murray was half attempting CPR and instructing Alberto to clean up, picked up rubber-topped vials, an IV bag and bottles from the floor. He hid all of these items in bags. According to Alvarez, Dr. Murray did not call 911 until the items were in the bags.
So here's the lesson kiddies. Don't go to med school and become doctors only to turn into complete sociopaths who care more about getting out of possible trouble than saving a dying man. Even if that man is a scary, skeletonized child molester.