TORONTO - "Entourage" star Adrian Grenier says he discovered the subject of his new documentary, "Teenage Paparazzo," during a chance encounter.

"I was looking for a summer project," says Grenier, 34.

"I was coming out of a restaurant one day and Austin -- who I thought was just a little boy -- turned out to be a shooter, a snapper, photographer, paparazzi. It was obvious that he was an amazing subject."

Grenier began to follow 13-year-old Austin Visschedyk with a documentary crew and in the process explored his own relationship with the paparazzi, something he'd pondered while rising to fame playing movie heart-throb Vincent Chase on "Entourage."

He wasn't the only celeb who'd noticed Austin. Lindsay Lohan, Paris Hilton and Eva Longoria had also encountered the pint-sized shooter, who jostled for position among veteran photogs at all hours of the night.

Many of the other paparazzos, Grenier discovered, seemed to respect the home-schooled teen, who sometimes travelled to celeb hotspots by bike or scooter, and often sold his photos for thousands of dollars.

While telling Austin's story, Grenier even tried out "papping" himself, much to the surprise of other shooters. He also interviewed media experts, longtime celeb photographers, and stars including Matt Damon, Rosie O'Donnell and Hilton, who admitted to a symbiotic relationship with the paparazzi.

"Teenage Paparazzo" shows Grenier in conversation with Austin, questioning the youngster about the ethics of his chosen vocation, and pressing the teen's parents on why they allow their son to do what he does.

"A lot of what this film is about is parenting, not only my mentorship of Austin, but also his parents who allowed him to pursue (being a) paparazzi at all hours of the night," says Grenier, in the city Tuesday for a round of media interviews.

At one point in "Teenage Paparazzo," Austin and his mother sit down with Grenier to watch segments of the film. The mother is clearly surprised to see her behaviour onscreen.

"I have a tremendous amount of respect for Austin's parents, not only for allowing me to make the film .... I also respect their ability to allow Austin to explore his world even though it may be dangerous," says Grenier. "I don't really look at it as a black and white thing."

The film also deftly illustrates how images shot by the paparazzi can create instant stories -- stories that can sometimes be manufactured.

Grenier interviews Hilton at length in the film and at one point they decide to stage a romp at the beach, delighting a waiting pack of photographers.

Those shots sparked a firestorm of rumours about their relationship.

"I had met her many years before I made the film," Grenier says of Hilton. "She is the queen of the tabloids. She's one of the original victims, subjects, artistes of the genre. Of course I wanted to interview her."

As the documentary unfolds, Austin receives increased attention. He is profiled in magazines, sought after for interviews and even offered his own reality show. And he likes it.

The scrutiny causes Grenier to fret about the sustainability of Austin's fame.

"This film was a hall of mirrors in a lot of ways," says Grenier.

"When I pointed my camera into that world, I thought I was looking at a destructive phenomenon of paparazzi and this little boy who's lost in it ... Ultimately, I found myself staring back at myself and realized I had to take responsibility for the images I was putting out there."

In the documentary, Grenier forges a tentative friendship with Austin, who ultimately makes some difficult decisions about his future.

"Teenage Paparazzo" is not the first documentary project for Grenier, who also produced the 2002 film "Shot in the Dark," about his search for his absentee father.

Grenier's perspective evolves during the shooting of "Teenage Paparazzo" and that aspect of documentary making is clearly something the star enjoys.

"I really believe that documentary film is such a vital and fulfilling and amazing genre," says the actor.

"When you put your camera and you point it out to world and ask a question, inevitably the answer will be revealed. It's just a matter of sifting through all the footage to find it."

"Teenage Paparazzo" opens Friday in Toronto and Vancouver.