Here's what we know, based on tweets from audience members, a comprehensive police scanner timeline on Reddit and media reports.
11:37 p.m.: Jessica Ghawi sends her last tweet from the movie theater. She was later confirmed dead by a friend on Twitter.
11:45 p.m.: Rachel Fedeli, who was in the auditorium next door to the theater where the shooter attacked, also tweeted her excitement.
Around 12:30 a.m.: Witnesses say the gunman, dressed all in black and wearing a gas mask, released tear gas and opened fire as soon as Batman first appeared on screen.
Around 12:30 a.m.: Bullets come through the walls of the theater next door — Fedeli's theater.
Around 12:30 a.m.: Amid the chaos, many were blocked from leaving the theater, where the suspect was believed to be still at large.
Around 12:45 a.m.: Outside the theater, even more chaos. People walk out splattered in blood.
Around 12:45 a.m.: Frantic 911 calls come in. Police try to piece together what happened.
1:27 a.m.: Overheard on the police scanner: "Bring as much crime scene tape as you can."
1:41 a.m.: First media reports emerge from 9news.
1:40 a.m.: 18 ambulances are on the scene, transporting victims to Denver Health. Ten people would die at the theater, while two would die at the hospital.
1:43 a.m.: Reports of a bomb going off in the theater. Bomb squad is onsite with K-9 units.