Matthew Mindler's cause of death has been revealed about two months after the actor's death was ruled a suicide.
Mindler died of sodium nitrate toxicity, the Lancaster County Medical Examiner's Office confirmed to TMZ. He was 19.
The medical examiner's office did not immediately reply to PEOPLE's request for comment.
The former child actor, who appeared in the 2011 comedy Our Idiot Brother, intentionally ingested sodium nitrate, a preservative that can be fatal when ingested in high quantities.
Jamie McCarthy/Getty Matthew Mindler in 2011
Mindler's mom, Monica, told TMZ she did not know her son was suicidal, and that she was speaking out to warn others of the dangers of sodium nitrate and its potentially lethal uses. Matthew bought $15 worth of sodium nitrate on Amazon, Monica said, telling TMZ the dose was enough to kill four people.
Matthew was initially reported missing in late August after disappearing from his dorm at Millersville University campus in Pennsylvania, where he was a first-year student.
He was found dead later that week when his body was located in Manor Township, near the Millersville campus. Matthew's death was confirmed by Millsersville President Daniel A. Wubah, who shared the news in a statement sent out to the campus community.
"This is a time of grief for the family, our campus and the community," his statement read, in part. "I ask that the campus community come together to support each other, and our students, during this difficult time."
At the time of his death, Matthew had not acted professionally in years, Monica told Pennsylvania newspaper The Morning Call. Along with his role in My Idiot Brother, he also appeared in As the World Turns, Last Week Tonight with John Oliver and Chad: An American Boy.
If you or someone you know is considering suicide, please contact the National Suicide Prevention Lifeline at 1-800-273-TALK (8255), text "STRENGTH" to the Crisis Text Line at 741-741 or go to suicidepreventionlifeline.org.