As police begin to piece together the events of the July 20 Denver cinema shootings which killed at least 12 and wounded 50, survivors of the massacre have begun to speak about their experiences.

Obed Sanchez was watching The Dark Knight Rises screening when the gunman entered the theatre: "It started, there were explosions behind me, there was dust, but I thought it was just a normal practical joke, you know, fireworks or something.

"But then I see people starting to leave the theatre and smoke behind me. For the first few seconds nobody was panicking, but then everybody started moving towards the exits, and we were being hurtled into the upper area of the theatre and from there you could see cops with shotguns and other weapons.

"I'm not sure what they were looking at because it was on the other side of the wall."

Meawhile, Jaime Marshall was in a neighbouring screen when she heard about the attack: "Some guy comes running in and he's running through the theatre, like the theatre's exits and he is like 'don't go out in the lobby, someone's shooting people out there.' And he runs out and at that point we still weren't sure if someone was pranking us or what so at that point we decided to leave.

"So we went up those stairs and we looked to the wall, to the side of the theatre where we heard the sounds from and there were bullet holes and so that's when we started screaming for all our friends just to get out."

She continued: "We went up the stairs and we were looking over the lobby and police were out there. There was one officer in a gas mask holding a huge rifle and they were just waving people, trying to get people through the lobby as fast as possible so we ran down the stairs, we ran out of the theatre. We walked out, I saw a girl with a bullet in her leg."

The shooter, a man in his 20s, was arrested shortly after the midnight attack.

The FBI said there was no indication so far of any connection to militant groups.