"There's a thin line between love and hate," said Jim Houran, psychologist with AETHOS Consulting Group and a published expert on celebrity culture and stalking
"From the fan's point of view they can feel, for a variety of reasons, a close personal connection with the celebrity. When they're presented with the reality their loyalty isn't reciprocated ... then you start feeling frustrated and the emotions come out that lead to more negative behaviours.
"In more extreme cases ... the identity of the fan really meshes with the identity of the star. "So if something good or bad happens to the celebrity the fan feels as if it's happening to them personally. And when that happens it's almost as if the fan wants to possess the celebrity — two [people] become one. And that's when you can see especially extreme behaviour — kidnapping, forced meetings. It's a desperate attempt to get and keep the closest connection possible."
For most celebrity stalkers, that connection will never be possible. And for those on the extreme end, the consequences can be dangerous.
"If you can't have that connection it feels as if you're losing yourself," Mr Houran said. "It's an addiction, they need more of the drug. And that propels more extreme behaviour."
It's this level of stalking that poses an "extreme danger", says Anthony Davis, founder of AD Entertainment Services. He's provided high level security to stars like Michael Jackson, Barbra Streisand, Sia, and Ariana Grande and says the situations can be deadly.
"Like with Sandra Bullock and the breaches at the homes of Taylor Swift, these suspects have ill intent. [They may possess things like] duct tape, a weapon. They show a premeditated attempt at some form of harm.
"You'll have certain stalkers who will operate and do things based on a sexual fantasy or some other form of perversion and others who are theoretically harmless — they just have a lovelorn type of adoration."
For many "celebrity worshippers", the obsession begins innocently. Mr Houran says it's a common assumption stalkers just have some form of mental illness. While that can be the case, he says it often starts with a fan looking for something positive in their life. But it spirals into a much darker place.
THE THREE STAGES
"It's just so delusional," Wendy Segall told BuzzFeed. As the Los Angeles County deputy district attorney, she's been responsible for prosecuting a number of high profile stalking cases — including Joshua James Corbett. "Or they believe that if the victim just sees them they will have this connection. They just have to meet and they will get to know each other," she said.
While the psychological states of a stalker can be separated into "absorption" and "addiction", Mr Houran said there are three stages the worshipper moves through.
The first is the entertainment and social phase, which is voluntarily escapism and can easily be turned off. The next is the "intense personal stage", where people start withdrawing. "That's when people start feeling a close personal relationship with the celebrity. This is when it starts to move into addiction," Mr Houran said.
In the third, "borderline pathological", phase, the addiction intensifies. Mr Houran says this is when impulsive behaviour and stalking begins. He said worshippers who reach this stage begin to have thoughts like: "If my favourite celebrity asked me to do something illegal as a favour, I would probably do it."
After Corbett was arrested inside Bullock's home, police found a cache of illegal weapons — including several machine guns — inside his home. Court documents state authorities also found a notebook and allege the notes detailed Corbett's plans to sexually assault the actor.
He had four photos of the star and a handwritten love letter, according to a search warrant affidavit. In the letter, he referred to himself as Bullock's husband and the father of her son.
Mr Houran said stalking doesn't always start out as malicious. But once stage three is reached, the high emotion can change their behaviour.
"At that level of celebrity worship you see a lot of impulsivity," he said. "I'm not surprised when people write strange letters and take things to the extreme. If people feel their attention and energy and loyalty isn't reciprocated, if they feel there are boundaries put in front of them on purpose by the star — that can be seen as rejection and that's when we see those more negative feelings come out."
THEY DON'T SLEEP
For stalking, arrests in California can't be made unless there's a "credible threat with the intent to place a person in reasonable fear for his or her safety".
"It's a situation where you can't depend on law enforcement until a crime has been committed — and that's too late," said Mr Davis. He said personal security for celebrities can range from tens of thousands of dollars per day to hundreds of thousands for around-the-clock detail.
"After they've broken into your house and stolen your possessions, then you call the police and there's things they can do," he said. "But if we research and find out who those stalkers are, we [security] can send letters and meet them and … we can intimidate them. We don't hurt them or threaten them … but make them know we know who they are. And often that's enough to make them go away."
According to The Journal of Forensic Sciences, two-thirds of stalkers pursue their subject at least once a week. Before breaking into Bullock's home, Corbett lurked outside her gate for days, according to court testimony.
A rash of Hollywood break-ins throughout 2017 highlighted just how easy it is to sneak inside the most private spaces of high-profile celebrities. Increased personal information available online has made it possible to get closer to celebrities than ever before — even inside their bedrooms.
Mr Davis said social media and entertainment news have increased the level of knowledge stalkers have on their victim. They know the geographical location of their subject throughout the day, who they're with and what their homes look like.
"[Stalkers] can Google map and see the perimeter of a celebrity's home," Mr Davis said. "They can pull up a blue print of the arena and figure out where talent will arrive, and exit so they can pretty much plan.
"They don't sleep. They constantly seek ways of penetrating the system."
