A gunman stormed into a movie theater in Aurora, Colo., early Friday morning, and opened fire on an audience watching a midnight showing of The Dark Knight Rises, killing at least 12 people and wounding as many as 50 more. Police have apprehended an alleged suspect, whom they've identified as 24-year-old James Holmes. The mass shooting is one of America's deadliest in recent history, and the death count is expected to rise; many critically wounded victims are currently fighting for life in hospitals. Calling on Americans to come together, President Obama vowed to bring the perpetrator to justice. Here, 4 takeaways from the evolving story:

1. The gunman was heavily armed
The gunman was carrying at least three weapons — a rifle, a shotgun, and a handgun — and possibly another handgun. He was reportedly wearing a gas mask, and released some sort of gas — tear gas, according to some reports — into the theater before beginning his rampage. The gunman "looked like an assassin ready to go to war," said Jordan Crofter, a witness. The suspect was easily apprehended in the theater's parking lot. "He did not resist. He did not put up a fight," said Frank Fania, a police spokesman.

2. At first, the attack seemed like part of the movie
Witnesses and victims say the theater was transformed into a scene of terror, with the gunman firing indiscriminately into a packed house filled with children and families. "Every few seconds it was just: Boom, boom, boom," says Jennifer Seeger, a witness. "He would reload and shoot and anyone who would try to leave would just get killed." Many witnesses say they thought the release of the gas and the initial bullets were a part of the movie. The bullets pierced the wall and struck movie watchers in the adjacent theater. Patrons saw stunned and bleeding victims emerge from the theater, with one describing a young girl's body carried out by a police officer: "She had been shot through her stomach, and the blood was just coming out. Her body was so limp. And her face, there was no life in her face."

3. The suspect's apartment is booby-trapped
Police have descended on James Holmes' apartment in Aurora, a suburb of Denver, but say the apartment is rigged with explosives and a "very sophisticated" booby trap. "We could be here for days," Aurora Police Chief Dan Oates said. The suspect has not made any statements, police say, and his motives remain a mystery. FBI officials, also involved in the investigation, have found no indications that the gunman was linked to any terrorist groups or had an accomplice. A portrait is beginning to emerge of Holmes, with reports saying he's a graduate student of neuroscience at the University of Colorado-Denver. He was reportedly in the process of withdrawing from the program.

4. Obama's reaction goes beyond platitudes
President Obama addressed the shooting in highly personal terms, noting that his two daughters also like to go to the movies. "What if Malia and Sasha had been in the theater as so many of our kids do every day? Michelle and I will be fortunate enough to hug our girls a little tighter tonight." Obama suspended his campaign events on Friday, and pulled down advertisements that that were scheduled to run in Colorado, as did his electoral rival, Mitt Romney. 

Sources: CNNThe Huffington PostThe New York Times, The Wall Street JournalThe Washington Post