Watch an exclusive clip of a new '20/20' documentary focusing on the murder of a promising actress

On July 18, 1989, promising young actress Rebecca Shaeffer was getting ready for an important meeting: Later that day, she was due to audition for a part in esteemed director Francis Ford Coppola’s film The Godfather III.

When her doorbell rang, Schaeffer was surprised to see a man she didn’t know — but who clearly knew her. In fact, Schaeffer had been the target of his obsession for years. Robert John Bardo, 19, had traveled to California from his Arizona home with the sole mission of stalking, and ultimately killing, Schaeffer. (He had hired a private investigator to locate her home address.)

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After a brief conversation, Bardo left, only to return a little while later. When Schaeffer opened the door this time, Bardo shot her once in the chest at point black range. She died in the doorway of her Los Angeles apartment building, just a few years after moving to California to pursue her dream of acting.

Next week’s special episode of 20/20, airing April 12 at 9 p.m. ET, is a two-hour documentary that shines new light on Schaeffer’s murder — and how the death of the up-and-coming actress, star of the popular sitcom My Sister Sam, ultimately changed the safety measures set in place to protect celebrities from stalkers. (Watch the exclusive clip from 20/20 above.)

Image zoom Rebecca Schaeffer CBS Photo Archive/Getty

Featuring a host of new interviews, the documentary will reveal fresh details about the nearly 30-year-old case.

Image zoom Getty Images

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Schaeffer’s slaying shocked the Hollywood community and led to the launch of a national anti-stalking movement that still exists today. Currently, there are anti-stalking laws in every state. Plus, after the murder occurred in 1989, L.A. police created the first U.S. team focusing on stalking investigations.

Police apprehended Bardo in Tucson, Arizona, the day after Schaeffer’s slaying. He was running through the streets admitting he had murdered her — and he had a photo of her in his pocket. He was convicted of first degree murder and received life in prison without the possibility of parole.