(NEXSTAR) – Late actor and comedian Paul Reubens was battling two types of cancer when he passed away in late July, according to a death certificate obtained by multiple news outlets.

Reubens’ primary cause of death was listed as “acute hypoxic respiratory failure,” as first reported by The Blast. Hypoxic respiratory failure occurs when the exchange of oxygen from the lungs to the blood is impaired, according to BMJ.

The underlying cause of death was listed as acute myelogenous leukemia (which affects blood and bone marrow), People reported. Reubens had more recently been diagnosed with metastatic lung cancer as well, indicating the cancer had spread to his lungs.

Paul Reubens
Comedian Pee Wee Herman, whose real name is Paul Reubens, admires his star on the Walk of Fame in Hollywood, Calif.ornia in this July 20, 1988 file photo. (AP Photo/Ira Mark Gostin, File)

Reubens, well known for his Pee-wee Herman character, passed away on July 30 at the age of 70.

In a posthumous statement shared to Instagram the day after his passing, Reubens revealed he’d been battling cancer for six years.  

“Please accept my apology for not going public with what I’ve been facing the last six years,” he said. “I have always felt a huge amount of love and respect from my friends, fans and supporters. I have loved you all so much and enjoyed making art for you.”

The day after his passing, Reubens’ team noted that be fought the illnesseses with “tenacity and wit.”

“A gifted and prolific talent, he will forever live in the comedy pantheon and in our hearts as a treasured friend and man of remarkable character and generosity of spirit,” they said of Reubens, in part.