Every day, some of Hollywood's biggest stars pay the price of fame, when obsessed fans become stalkers, fixated on a fantasy that to them is very real. And in Los Angeles, ground zero for celebrity stalking, the police department has a one-of-a-kind "threat management unit" to handle those cases.
Actress Jennifer Garner recently got a permanent restraining order against a man who blogs about human sacrifice. She says he has terrorized her since 2002.
Michael Douglas' stalker threatened to cut up the actor's wife, Catherine Zeta-Jones, and feed her to her dogs.
Uma Thurman describes her experience with a stalker -- who was convicted in court -- as a nightmare.
And in the case of Brad Pitt, a woman once broke into his home, fed his dogs and slept in his pajamas.
Many celebrities are not overtly threatened by their stalkers, but the ordeal can still be terrifying.
The Los Angeles Police Department's team of highly trained detectives -- known as the threat management unit -- first banded together because of one star's violent death in 1989.
Rebecca Schaffer was a rising star with a lead role on the hit TV show "My Sister Sam" when she was murdered by an obsessed fan named Robert Bardo. Back then, there were no stalking laws in California or anywhere else.
Schaeffer was gunned down at her front door, and for California police officials, her brutal death was a wake-up call.
"She had to be the victim of a homicide in order for us to get the message that something needs to be done in the way of legislation to address stalking crimes," said Detective Jeff Dunn. "There is a fine line between fan and fanatic."
Dunn began what would be a long and often shocking career, working with celebrities to investigate the most aggressive stalkers.
"They've got access to a telephone and a computer and they can make our victims' lives a living hell," said Dunn.
In 2003, Britney Spears was followed by an obsessed fan. Masahiko Shizawa embarked on a 37-city obsession tour in pursuit of the recording artist.
"What we had was a Japanese business man, came to America on a tourist visa for the sole purpose of following Britney Spears around on her concert tour," said Dunn. "As far as [Spears] is concerned, he was completely delusional."
Dunn believes Shizawa used the Internet to not only track Spears' concert schedule, but her life from Louisiana to Los Angeles.
"We weren't aware of this guy until he showed up at her Hollywood Hills home and confronted the security guards," said Dunn.
Shizawa had been following Spears from the front row of dozens of concerts. Dunn says he traveled to her home in the South, and to her mansion in Hollywood. He sent the pictures to prove it.
"You can see he was in very close proximity to her at several points in time," Dunn said, shuffling through the photos. "Here's one that if you were Britney Spears you would find very concerning. Here's a picture of her limousine as she is leaving one of the concert venues and on the back of the photograph he says 'I'm chasing you.'"
Detectives say the most dangerous part is that Shizawa believed he had a relationship with Spears.
"We knew there was going to be a long-term problem until she dealt with it," said Dunn.