Fans now know what killed actress Margot Kidder.

The Park County Coroner's office ruled the "Superman" star's death a suicide, The Associated Press reported.

Kidder was found by a friend in her home in Montana in May.

Her manager, Camilla Fluxman Pines, said Kidder died peacefully in her sleep.

But Coroner Richard Wood said that Kidder, 69, “died as a result of a self-inflicted drug and alcohol overdose.”

He said via a statement that no other information would be released.

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Maggie McGuane, Kidder's daughter, told the AP that she knew her mother died by suicide.

"It's a big relief that the truth is out there," McGuane told the AP. "It's important to be open and honest so there's not a cloud of shame in dealing with this."

Kidder was one of several recent suicides by well-known celebrities this year. Others include celebrity chief Anthony Bourdain and fashion designer Kate Spade.

Kidder was said to have struggled with metal illness for many years. The AP reported that it was made worse in 1990 after a car accident left her in debt and eventually led her to use a wheelchair for nearly two years.

She had also been diagnosed with bipolar disorder. A manic episode in 1996 left her homeless for a period of time, People magazine reported.

Kidder's career stretched from the late 1960s through 2017, but she was most known for the four "Superman" films between 1978 and 1987, in which she portrayed Lois Lane, she also appeared in "The Amityville Horror" in 1979. Recently, she appeared on "R.L. Stine's the Haunted Hour."

FILE PHOTO: Actress Margot Kidder signs autographs at Comic Con International July 14, 2005 in San Diego, California. The cause of death for Kidder, who died in May, was released after being declared a suicide.

Credit: Sandy Huffaker

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Credit: Sandy Huffaker