"IN AN INSTANT," AIRING ON "20/20," FRIDAY, APRIL 19 ABC

In a moment of crisis, lives can change drastically by twists of fate and split-second decisions. "20/20" reports on surviving everything from random violence and acts of terror to massive highway accidents and the madness of crowds and stampedes, FRIDAY, APRIL 19 (10:01-11:00 p.m., ET) on the ABC Television Network.

ABC News Correspondent Byron Pitts will give viewers the latest information on the Boston Marathon tragedy, including stories of survival. Additional reports will include:

· John Qui�ones reports on the split-second decisions that can make the difference between life and death during a potentially deadly highway pile-up.

· What makes the difference between life and death when there is an active shooter in the office? Elizabeth Vargas speaks with workplace shooting survivors and a law enforcement official who demonstrates what to do.

· "20/20" explores the phenomena of "crowd think" and the herd mentality of stampedes, where individuals forget logical thinking and instead follow everyone else -- even if it is clearly not the right thing to do.

· Amputee college soccer player Bree McMahon shares her inspiring story of recovery, and "20/20" is with her as she visits Boston to support the amputee victims whose lives changed in an instant on Monday. Deborah Roberts reports.

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is executive producer.