The Washington, D.C. Chief Medical Examiner has released the cause of death in the sudden and shocking death of Hawthorne Heights rhythm guitarist Casey Calvert last month.

According to a report obtained by MTV, the examiner listed Calvert's death as accidental, though it added that it was brought on due to "substance abuse." Both citalopram (also known by the brand name Celexa) and clonazepam (also known by the brand names Klonopin and Rivotril) are prescription drugs, the former an antidepressant and the latter used to treat seizure disorders and panic attacks.

Calvert was found dead on Hawthorne Heights' tour bus outside the 9:30 Club in Washington, D.C., on November 24.

Update: It is important to note that prescription drug interactions are often complex and can pose significant dangers even when the amounts used are within doctor recommended guidelines.