"This death could've been preventable," Assistant Chief Ed Winter tells PEOPLE. "Murphy was planning on seeing a doctor, but she unfortunately passed away before she did. This was a case of a person with pneumonia who was anemic (having a low blood count) who was taking medication when she should've been getting medical treatment."

Chief Coroner Investigator Craig Harvey specified that pneumonia was the primary cause of death, with drugs and anemia as contributing factors.

Winter confirms that no illegal drugs were found in the actress's system: "It was only prescription and over-the-counter meds," he said.