Twelve have been killed and about 50 wounded in a mass shooting at a movie theater outside of Denver. A gunman wearing a gas mask and bulletproof vest set off what appeared to be a smoke bomb before opening fire. Police say the suspect is in custody and that he is believed to have acted alone. The attack came at a screening of the new Batman film in the Denver suburb of Aurora. A number of the wounded are in critical condition. It was the worst mass shooting in the United States since the killings of 32 people at Virginia Tech five years ago.