The medical examiner’s office revealed that Catherine O'Hara's immediate cause of death was listed as pulmonary embolism, with rectal cancer as the underlying cause.

Catherine O'Hara's manner of death revealed as pulmonary embolism, with rectal cancer named as underlying cause;

Sources confirmed to NBC4 Investigates in Los Angeles that pulmonary embolism was the immediate cause, with rectal cancer as the sequential cause of death.