Breaking Down The Boston Marathon Bombing

Three are dead and at least 140 are injured after two bombs blasted the marathon finish line.
2:52 | 04/16/13

Coming up in the next {{countdown}} {{countdownlbl}}

Coming up next:

{{nextVideo.title}}

{{nextVideo.description}}

Skip to this video now

Now Playing:

{{currentVideo.title}}

More information on this video
Enhanced full screen
Explore related content
Comments
Related Extras
Related Videos
Video Transcript
Transcript for Breaking Down The Boston Marathon Bombing
We were able to reconstruct it all moments and quite terrifying moment. Attack appears to -- Just before two feet -- PM this is the viewpoints -- by maybe 26000. Marathon runners we're approaching the finish line. First of -- Rocks sidewalk along force white's book blasting. Metal barricades in the streets. -- crowds gathered. Just as the -- -- approaches before our intent. There -- about -- bill. Twelve seconds later as many -- to see him up at. A second explosion goes up. -- 130 yards in the first less than a block away. Very -- -- -- round here keeping it. He was going down for you. Injured lay on the pavement blood -- the ground. Emergency medical technician. Boston Police and some 400 national Guardsmen already on the race. Does the defense medical -- -- transform its promise. Saw one guy with his legs -- needs some -- Shrapnel wounds and people decide that ahead. Like 3 PM just as the president is being briefed on the attacks reports trickle -- of yet another explosion. This time at Boston's JFK library it's later. There are reports of additional devices several schools and hospitals -- -- Meanwhile over 130. Victims are being transported to six area hospitals just after 6 PM. President Obama addresses the country. Valley. To find those responsible and make no mistake we will get to the bottom of this any responsible individuals. Any responsible group's. Appeal -- -- The justice. Matter how many times you see it's still just as terrifying you want to show. A one photographing as well -- speaking. To what it was knots. The hundreds and hundreds of bags waiting for runners who were never able to claim them. Again a snapshot. Innocence and perfection on that patriots day. Suspended if not lives.

This transcript has been automatically generated and may not be 100% accurate.

{"id":18966273,"title":"Breaking Down The Boston Marathon Bombing","duration":"2:52","description":"Three are dead and at least 140 are injured after two bombs blasted the marathon finish line.","section":"GMA","mediaType":"Default"}