Four people are dead after a police standoff involving a gunman in the U.S. city of Aurora, Colorado, the site of a deadly mass shooting at a movie theater last year.

Police say the suspect in Saturday's shooting barricaded himself inside a house before he was shot and killed when police entered. It is unclear whether the suspect shot himself. Police found three other people shot and killed inside the home, while one person escaped from the house uninjured.

Aurora made international headlines last July when a man went on a shooting rampage inside a movie theater during the midnight screening of the latest Batman film, The Dark Knight Rises. The attack killed 12 people and left at least 58 others wounded.

Police say suspect James Holmes threw a tear gas bomb in the theater before opening fire on the audience.

Prosecutors have filed 142 charges against Holmes, including counts of murder with extreme indifference, attempted murder and possession of explosives. His preliminary hearing is scheduled to begin on Monday.

The cinema shooting re-ignited the U.S. gun control debate, which intensified last month after a gunman killed 20 young children and six staff members at an elementary school in Connecticut.