Some of the first images spread quickly through YouTube, Twitter and Facebook. The impact of social media is highlighted on days like this, where millions flock to sites to share their feelings and get in contact with loved ones.
It's where millions of people get their information every day: Their smart phones.
One of the first cell phone videos from the movie theater to hit the Web moments after the suspected gunman opened fire on patrons in the Aurora, Colorado, movie theater spread quickly across sites, like Facebook and Twitter, and was viewed by people across the globe.
That's how Twitter user Annie Gerker found out.
"It had a whole feed about it, and I had no idea, so I clicked it and watched the video," said Gerker.
DePaul Media Studies Professor Paul Booth believes many people learned about the massacre from their smart phones and social media sites.
"The minute that something massive like this happens, it just spreads, the information spreads across Webs of networks of people, friends acquaintances and even news sources," Booth said.
Some victims that were there shared their experiences and updated friends and family with posts.
Aspiring sportscaster Jessica Ghawi was among the victims killed in the shooting. She posted on her Twitter account Thursday night that she was going to see the midnight showing of The Dark Knight Rises with a friend.
Just last month, Ghawi escaped a deadly shooting at a Toronto shopping mall , writing online how she felt empty, and asked, Who would go into a mall full of innocent people and open fire?
After receiving the news of her death, Ghawi's brother Jordan took to the Internet to share details, that his sister was shot multiple times and died after a gunshot wound to the head. Her friend was also injured and remains in critical condition.
Jordan has been updating his posts online all day long for those sharing their concern to the family.
Professor Booth says it is not uncommon for victims or their loved ones to share updates on social media.
"Think of all of the families of the people in that theater who check Twitter to see if their loved ones are OK," said Booth. "I mean, obviously our hearts go out to those that aren't, but for the hundreds that are OK, it's great that they can check in instantaneously."
Other victims inside the theater posted on social media that when they first saw the tear gas smoke rise up they thought it was special effects. Then shots rang out and they realized there was a gunman inside the theater.