Transcript for Manhunt on after deadly Barcelona attack

Next tonight, the deadly terror attacks. After Barcelona and the white van plowing through the crowd, another attack. And a hero policewoman, reportedly killing 4 out of 5 attackers on her own. Tonight, we're learning about the American husband and father of three back in Barcelona who was killed. James Longman from Spain again tonight. Reporter: Overnight, the second horrific scene of terror. Another car barreling into a crowd in the Seaside town of cambril, Spain, killing one and injuring six. This video capturing the tense moments as officers engage one attacker armed with a knife. Police say a hero policewoman taking down 4 of the 5 terrorists killed. Here you can see the man wearing what police thing might be a suicide vest. Shot after shot, he drops to the ground. Only to get up again. Lunging toward police. They finally take him down. And that bomb vest? A fake made of soda cans. Used, terror experts believe, so he would be killed, not captured. It came just hours after that white van jumped the curb in Barcelona, zig-zagging down that pedestrian path. Killing 13 and wounding at least 120. Newly released surveillance video shows the moment. You can a mother with a stroller narrowly escaping. One of the people in that crowd, mother Sherie Weiss from los Angeles telling David about the moment she saw that van speeding towards her. And we know you're a mom and it would seem a mother's instinct kicked in because you described actually grabbing a child who was fren as this was all playing out and trying to get him out of the way. When I realized I had to jump to my right, I saw a 14, maybe 15-year-old boy like a deer in headlights. He just froze and I could tell in his face he didn't know what to do so when I jumped to the right I pulled him and pulled him behind a pole with me and we crouched down together. Reporter: She saved him as she witnesses a man next to them get him. Tonight were learning more about the lives lost. One of the victims Jared tucker, father of three from San Francisco. There in Spain to celebrate his first anniversary. Separated from his wife while souvenir shopping. And 7-year-old Julian Cadman from Australia. Tonight, the police making new arrests on the trail of an ISIS inspired terror cell. As they search for these four suspects, the most wanted men in Europe. This is Ripoll. It's a small town of about an hour north of Barcelona and it's where many of the attackers are from. The hometown of Moussa oukabir, the 17-year-old who they believe stole his brother's I.D. To rent the white van used to plow into those crowds. The possible driver. Back in Barcelona, just 24 hours after that horrific attack crowds on that promenade chanting, "We are not afraid." Shaken but defiant. And James joins us live tonight. So many back out there sending a message, and still a fast-moving investigation tonight? Reporter: It may look like life is back to Normal here, but this is still very much a city on edge. Authorities can't be sure of the full extent of the terror group, what they might have had planned next, and who was involved. Thank you. Meantime, we're learning the

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