SEATTLE, July 28 — True-crime author Ann Rule has died. She was 83.

Rule’s daughter, Leslie Rule, wrote in a Facebook posting that her mother had many health issues, including congestive heart failure.

“My mom died peacefully last night (Sunday). She got to see all of her children, grandchildren and great grandchildren,” she said.

In a statement, a spokesperson for CHI Franciscan HealthRule confirmed Rule had died on Sunday at the Highline Medical Centre in Burien, Washington. The cause of death remains unknown.

Rule first found the spotlight after she published her first and most famous work, “The Stranger Beside Me”, in 1980.

In it, she profiled serial killer Ted Bundy who was her former co-worker on the late shift at a Seattle suicide hotline.

The book has sold more than two million copies, and Rule went on to publish dozens of bestselling true crime novels over the decades.

Rule’s final book, “Practise to Deceive”, was published in 2013. On her website, it says that she wrote more than 1,4000 articles, mostly on criminal cases.

In a 1998 interview with the LA Times, Rule said she struggled with crime writing, seeing it as an ethical dilemma. “I thought: ‘Oh my God, I’m making a living from somebody else’s tragedy. Can I do this?’

“I really care about the people I’m writing about... I finally came to the knowledge I’m doing what I probably was meant to do in life.”

As a result, Rule became a staunch advocate for the rights of victims of violent crimes.

Carolyn Reidy, president and chief executive officer of Simon & Schuster, said in a statement, “By deciding to focus her books on the victim, Ann Rule reinvented the true crime genre and earned the trust of millions of readers who wanted a new and empathetic perspective on the tragic stories at the heart of her works.”

The Associated Press said Rule was born in 1931 in Lowell, Michigan. She earned a bachelor’s degree from the University of Washington in creative writing, with minors in psychology, criminology and penology.

According to The Hollywood Reporter, Rule worked briefly at the Seattle Police Department when she was 21 and began writing for magazines such as True Detective in 1969.

Over the course of her career, the FBI and the US Justice Department also turned to Rule for her expertise on serial murders, such as the Green River Killer case.