the big countdown and what a year it was. Tonight our journey with all of you from boston strong to the strongest little superhero we could find. Reporter: It was a beautiful and proud april day in... See More
the big countdown and what a year it was. Tonight our journey with all of you from boston strong to the strongest little superhero we could find. Reporter: It was a beautiful and proud april day in boston when the first one hit. Then the second one. Two homemade bombs ripping through the crowds at the finish line of the boston marathon. Everybody started running, panicking, then another bomb went off. Reporter: Killing three and wounding nearly 300. Make no mistake, we will get to the bottom of this. Reporter:26-year-old tamerlan tsarnaev and his younger brother, 19-year-old dzhokhar tsarnaev. An m.I.T. Police officer shot and killed. Reporter: The older brother, tamerlan, killed, too. A boston suburb on lockdown. Police move in. They were saying, you got them. Boston pride, boston strong. Reporter: America would soon turn to another city, cleveland. The nation hearing the 911 call ten years in the making. Help me. I'm amanda berry. I've been kidnapped. I've been missing for ten years. Reporter: Amanda berry disappearing at 16, making that brave call, at 27 years old. Three women trapped inside, all held captive by ariel castro. Castro fathering a baby with amanda. This is the moment that this community has been waiting for, for ten years. Reporter: We were there the day amanda berry came home with her 6-year-old daughter. AND gina DeJesus flashing a thumb's up. Those young women, survivors. There has been some kind of crash at san francisco international airport. Reporter: Incredibly, more than 300 people survived this, an asiana 777 cashing. A pilot training on that aircraft landing far too short. The back of the jet breaking off. Over my shoulder here you can see the burned out fuselage. Reporter: And in a cruel twist of fate, one teenager survived the crash, only to be run over by not one but two first responder trucks. For the survivors in moore, oklahoma, tearful reunions, two elementary schools wiped out and one of the teachers following her own instinct, rushing the kids to the bathroom. It's almost over. It's almost over. Reporter: The brave teacher, mrs. Dziedzic, brought us back to that school. Oh, my god. Reporter: She'll never forget. In all of the madness, suddenly finding her son looking up at her. Honey, it's okay. Reporter: There were prayers around the world this year from catholics waiting to meet their new hope. We are looking at the smoke billowing out of the cast iron chimney above the sistine chapel. Reporter: Jorge bergoglio taking the name francis, inspired by st. Francis of assisi, known for his compassion for the poor. He even let this little boy, a stranger, steal the spotlight on stage. And then his chair. At summer's end americans suddenly learned we were on the brink of war. Did the syrian government use chemical weapons against its own people? Reporter: There was a shock when these images were revealed. The children gasping for air. The united states should take military action. Warships at the ready. Reporter: Russia stepping in, negotiating a deal with syria to give up its chemical weapons. 2 million syrian refugees. We met so many of the children waiting to go home. You're thinking about your father? It's okay, sweetie. Reporter: A sudden breakthrough elsewhere. Iran electing a new president who would travel to america and speak before the u.N. And speak on the phone with president obama. History was made today, diane. Reporter: Then a landmark deal beginning to curb tehran's nuclear program in exchange for something else, easing those crippling economic sanctions we heard about in tehran. Day to day increasing prices. You see it day to day. Yes. I believe we must test it. Reporter: And one another victory. For a different kind of super power. In san francisco, that cape crusader who gave that thumb's up. Little miles, diagnosed with leukemia, granted a wish by make a wish. He wanted to be batkid for a day. His dad remembers the knock at the door. Batman knocked on our hotel door holding a costume and told miles you got to go to work. Reporter: The choppers overhead. Watching batkid save the day. The whole city in on it. And from the mayor. Thank you, batkid. Reporter: Bat kid, suddenly realizing his power. Watch this. The same trademark confidence he showed us, a superhero just when we needed one. He saved the day and left us all smiling. Our look back tonight at 2013.
This transcript has been automatically generated and may not be 100% accurate.