During the final months of her life, Monroe lived at 12305 Fifth Helena Drive in the Brentwood neighborhood of Los Angeles. Her housekeeper Eunice Murray was staying overnight at the home on the evening of Saturday, August 4, 1962.Murray awoke at 3:00 a.m. on August 5 and sensed that something was wrong. Although she saw light from under Monroe's bedroom door, she was unable to get a response and found the door locked. Murray then called Monroe's psychiatrist, Dr. Ralph Greenson, who arrived at the house shortly after and broke into the bedroom through a window, finding Monroe dead in her bed. Monroe's physician, Dr. Hyman Engelberg, arrived at the house at around 3:50 a.m.and pronounced her dead at the scene. At 4:25 a.m., they notified the Los Angeles Police Department. At last they later discovered that Monroe died between 8:30 p.m. and 10:30 p.m. on August 4,and the toxicology report revealed that the cause of death was acute barbiturate poisoning.
CIA director John A. McCone was suspicious. Sending antiaircraft missiles into Cuba, he reasoned, "made sense only if Moscow intended to use them to shield a base for ballistic missiles aimed at the United States". On August 10, he wrote a memo to Kennedy in which he guessed that the Soviets were preparing to introduce ballistic missiles into Cuba.
On August 31, Senator Kenneth Keating (R-New York) warned on the Senate floor that the Soviet Union was "in all probability" constructing a missile base in Cuba. He charged the Kennedy administration with covering up a major threat to the US, thereby starting the crisis.