Sandy Dahl, the widow of United Flight 93 captain Jason Dahl, died of heart failure brought on by an accidental drug and alcohol overdose, according to an autopsy released Friday.

Dahl passed away unexpectedly in her sleep in May. She was staying at a friend’s home in Lakewood at the time.

According to her autopsy report by the Jefferson County Coroner’s Office, Dahl’s death was “consistent with the combined impact of alcohol and multiple drug toxicity.”

A heart condition also possibly contributed to her death. Alcohol, painkillers, anti-depression and anti-anxiety drugs were found in her system, according to the report.

Jason Dahl was the Captain of Flight 93, which crashed into a Pennsylvania farm field on Sept. 11, 2001, as terrorists tried to hijack the plane and passengers and crew members fought back.

After her husband’s death, Sandy Dahl became a powerful advocate for preserving her husband’s memory and honoring the heroism of those aboard Flight 93. She gave frequent speeches and founded a scholarship fund in Jason’s honor to provide money for aspiring pilots.

The tragedy, though, continued to weigh on Dahl. In an interview last year with The Denver Post, Dahl said she sometimes awoke from nightmares or found herself grinding her teeth for no reason. She said counselors had told her she had post-traumatic stress disorder.

“Normally, people have a memorial, and it’s behind them then,” she said. “This is never going away.”

After Dahl’s death, Patrick White, the president of The Families of Flight 93, praised Dahl’s bravery following her husband’s death.

“Sandy’s courage picked up where her husband’s left off,” White said in a statement. “Her dedication to completing the Flight 93 National Memorial as a way to honor her husband’s heroic actions on 9/11, and those of his fellow crew members and passengers, is a significant part of her legacy.”

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold