The first trailer for I Am Heath Ledger - a documentary about the late actor - has been released and it's predictably heartbreaking.

Much of the footage was shot by Ledger himself, and the trailer shows several shots of him with a handheld camcorder in his hand.

"There were always cameras around, a video camera, a Polaroid camera or the film camera," model Christina Cauchi says in the trailer. "That's the only way I think of him."

Musician Ben Harper, who also appears, says: "Heath was the most alive human, and if it wasn't on the edge, it didn't interest him."

The full documentary will premiere at Tribeca Film Festival on 23 April, just over nine years after his death in 2008 aged 28.

Directed by Derik Murray, it includes never-before-seen footage of the actor, along with tributes from his friends, family and colleagues.

Ang Lee, who directed Ledger in Brokeback Mountain, says: "Even as a supporting actor he will steal the whole show. That's the power of Heath Ledger."

"Before Brokeback Mountain came out it would have been unthinkable to have a romantic tragedy involving two gay cowboys. This is one of the biggest heartthrobs on Earth taking on that character - that's an artist," Australian actor Ben Mendelsohn says.