"We learned today the combination of drugs in Michelle's system, along with a condition we were unaware of, proved lethal," the actor and comedian wrote in a statement to the Associated Press on Friday.
Oswalt went on to explain that when the couple married in 2005 he had no idea she had an underlying condition that caused blockages in her arteries.
The blockages, combined with her taking the medications Adderall, Xanax and the pain medication fentanyl, caused the mother of one's death in April 2016, Oswalt said.
According to Los Angeles coroner's Lt. David Smith, McNamara's cause of death is still listed as "pending."
Our thoughts and prayers are with Oswalt and his family at this time.
Originally posted on Womanista.com.