From Halopedia, the Halo wiki
Peter Jackson is a New Zealand-born filmmaker. Jackson is best known as the director of The Lord of the Rings film trilogy, as well as its prequel, The Hobbit film trilogy which he, along with Fran Walsh and Philippa Boyens, adapted from the novels by J.R.R. Tolkien.
In 2006, Jackson formed WingNut Interactive, a video game development studio, in partnership with Microsoft Game Studios. The studio's first project was to develop and produce Halo: Chronicles, an interactive story-telling game which was later cancelled .
In 2008, Peter Jackson was announced as the executive producer for the Halo film. He was also initially hired as the director for the film, though it was later announced that director Neill Blomkamp would be helming the project, due to Jackson's other commitments.
When plans for the film fell through, Jackson and Blomkamp instead started production on District 9. Many elements from the cancelled Halo film were re-used or adapted for District 9, including the basic Warthog and Pod infector designs.