Virginia Tech shooting survivor works to prevent future tragedies

ARLINGTON, Va. -- Before the Orlando nightclub massacre claimed 49 lives, the April 2007 shooting at Virginia Tech was the deadliest mass shooting in U.S. history.

In an iconic photograph from Virginia Tech, two police officers are seen carrying Kristina Anderson from Norris Hall shortly after she had been critically injured by gunman Seung-Hui Cho.

To this day, Anderson remembers Cho vividly.

"He had two guns. He had a 9 mm and a .22," Anderson told CBS News. "He was shooting people one by one by one."

Cho shot Anderson three times.

"I told myself to hold on and to stay very low," she said. "I pretended to be dead."

In all, 32 people were killed that day. Since her recovery, Anderson has been working to prevent another mass shooting, helping to develop a smartphone app called LiveSafe.

With the app on their phone, someone in danger doesn't have to call for help but can simply text police dispatchers directly -- and even send pictures.

Had the technology been available at Virginia Tech, Anderson said it may have saved lives.

"Law enforcement could have received tips, 'Here is where to go,' we could have shaved seconds off the response potentially as well," she said.

The app is now being used by large corporations, school districts and universities across the country. Users can report anything from a suspicious person to an assault or a shooting.

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The LiveSafe app Kristina Anderson helped develop.

CBS News

Jay Gruber, the chief of police at Georgetown University, said a map shows police where help is needed.

"We immediately see where the caller is," Gruber said. "And before we can even begin to ask them, 'Where are you?' we can already send officers to that location."

Anderson said reacting quickly is key to stopping future attacks.

"He fired 174 rounds, 61 were in my classroom," she said. "It was very, very quick."

She remembers how fast her life changed.

"I have no space to waste time or be negative about things or not take any actions that I think are possible to prevent the next one," Anderson said.

Virginia Tech is among the schools using her app.