Twelve people were killed and 59, including a 3-month-old child, were injured when a gunman opened fire in a Colorado movie theater during a midnight showing of "The Dark Knight Rises" early Saturday morning, police say.

KUSA out of Denver reports witnesses saying that the theater went dark, and the movie began. They heard a metal canister fall, and then a hissing noise. The theater began the fill with what police are now saying was tear gas, and then the man, now identified as 24-year-old James Holmes, opened fire. The bullets killed 10 instantly, and some went through the walls to other theaters, police said.

Police said they believe Holmes was working alone on this violent attack. More as this story develops.

Watch as this witness describes the events in the theater.

[Via KUSA]