rocking paris to i i core. and how one man and his piano is touching hearts around the globe

"imagine" uniting the good evev. thanks for joining us.

a worldwide terror crackdown under way. the target, one mastermind and the terror network behind the paris attacks. mo than 150 raids,s, dozens of arrests. the president of france declaring war on isis. launching air tribes. but there is skepticism at home about syrian refugees as isis issues new threats against america. abc's chief foreign correspondent terry moran is on the ground in plus sells. brussels. >> reporter: warnings of more attacks on u.s. soil issued by is militants in a batch of new propaganda videos saying, as we struck france in the center of its abode in paris, we swear we will strike america at its center in washingtonon cia director brennan says the attacks in france should serve as a wakeup call for americans. >> their agenda is to kill. pure and simple. >> reporter: the threats come aftetethe u.s. helped france organize an air strike that pounded the de facto isis

and today the noose tightened around the isis fighters responsible for the carnage in paris. seven attackers confirmed dead but at least one remains at large. 26-year-old la saw abdel slam, now perhaps the most wantedan in the world. a french national born in brussels he's believed to be the gunman who led the team shooting in restaurants and bars that left bodies out in the open streets. this morning police thought they tracked him to this building in n the gritty neighborhood outside brussels molenbeek. police cordoned off streets, surrounding an apartment buildi, scaling rooftops. then t ty moved in. but their target was gone. police say he fled paris friday night. they found the cars he'd rented. one left outside the theate suburb. then driving a third car with two other passengers, he headed toward belgium, stopped by police at a roadblock on detained. and they made it across the

border. the two other people in that car picked up by police later, now charged with participation in terrorism. and the fugitive's brother detained but later released saying he had no idea that both his brothers -- one died during the attacks -- were terrorists. "we are an open-minded family, we never had any problem wills jut advertise." we do not know if he will h he the cocoage to t tn himself in. he you up here, he is a normal person." abdel slam is among muns in belgium who have joinedd isis or other terror organizations. a fert ground for extremists. we spoke to a resident who's seen this firsthand. three of your neighbors went to syria? >> right. >> reporter: after 12 people were killed by three gunmen in the "charlie hebdo" attacks, in paris this past january, authorities traced the rifles used back to belgm.

making this coury a critical link in past plots. hasan rahali is a city councilor here. >> is it a cancer or disease in this neighborhood? >> it's a disease now. it's bece a disease. >> reporter: he tells us how discrimination against muslims may have radicalized many young men. >> there are things that remind you you're different. you' coming from somewhere. you're second. there's the first l lel and the second level. >> second chas? >> second class. that's really the problem. >> when you were young and you felt the sting of discrimination, when you fel the pain -- >> hopeful, hopeful. you know, this desire, desire to beat. desire to make something bad. you are so -- the frustration in you, you need to expose it. >> you felt that? >> yeah, absolutely, in my heart. deep in my heart.

massacre,, officials now crackingg down on these jihadist hotbeds. in france, 168 police raids took place. in all, 31 weapons and computers seized. 23 people have been arrested and questioned. another 104 placed under house arrest. authorities believe the plan was organized in belgium, carried out in france. but masterminded in syria by this man. 27-year-old abdel hamid aboud, linked to previous terror plots including the foiled european train attack earlier this year.% >> isis is much larr than al qaeda ever was. and certainly much more powerful today than al qaeda is. they are more well trained. they are more well funded. and they control much more territory than al qaeda ever did. >> reportete isis is believed to have 20,000 to 30,000 fighters financing their terror. oil fields that generate about $40 million a month.

and now with the paris attacks the group signaling to the world that it's operating on a global scale, prompting france's president francois hollande to order the country's biggest raids in syria to gate. the targets an isis command post, training camp, recruiting center, weapons warehouse. areas the u.s. identified and passed along to france. we are at war with jae haddist terrorists, hollande said. in the last 15 months the united states conducted the majority of the more than 8,000 air strikes in iraq and syria, committed 3,500 troops to iraq, and 50 u.s. special operations troops. but critics now say it's not enough. earlier today president obama responding to multiple questions about his strategy against isis. >> t tre will be an intensification of the strategy that we put forward. but the strategy that we are putting forward is the strategy

>> president obama, after the paris bombings, seems intent on doubling down on a losing strategy. that's not going to work. a few more air strikes are not going to eviscerate a group as determined and as entrenched as the islamic state. we need a new strategy to mobilize the sunnis who form the popular support base for isis. we n nd to turn them against isis. as we previously turned them against al qaeda in iraq in 2007. >> reporter: the attacks, the new threats and reports that one of the paris attackers may have slipped into france as a syrian refugee have forced the u.s. to ramp up security. a growing number of states are now refusing to take in those refugees. potentially affffting the 18,000 cases referred by the u.n. for refugee resettlement. >> we can't be in a position where we abandon our belief in refugee asylum because of thee possibility that there might be

one terrorist hidden in the group. we have to do very thorough vetting and if they cannot be fully vetted they're not allowed in. this country standss for takinin in refugees and asylum seekers. and for us now to abandon that is to do exactly what the terrorists want us to do. >> reporter: while cities across the u.s. are now on high alert in new york city a heavy police presence in times square. >> beer here to prevent, detect, deter, disrupt. >> reporter: concerned after the pari attacks. for "nightline" i'm terry moran in brussels. >> our thanks to terry moran reporting from brussels tonight. we're joined by abc's chief justice correspondent pierre thomas. the intelligence community is clearly concerned that the jihadists seem to plot the attacks undetected. >> juju, there are real concerns about what's called the growing dark syndrome. officials worry the killers in france may have used encryption technology to hide their computer and cell phone communications.

new tonight belgian officials suspect the terrorists used gaming systems like playstations to communicate off the grid. all disturbing because it appears the bad guys were invisible. >> thanks, pierre. deeply disturbing. pierre thomas in washington. up next the dramatic survivor stories emerging from paris.

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it was a festive friday night. what a cosmopolitan city like paris does best. romantic outdoor cafes, soccer match, a r rk concert. all shattered by terror. tonight powerful stories and images of survival emergeing amid the bloody chaos. abc's matt gutman is in paris night. >> reporter: it's been three days since paris' rupted in gunfire. the worst across the street from here at the bataclan theater. as parisians continue to mourn

the survivors, initially too traumatized to speak, are beginning to tell their stories. the crowds raising a glass to the band. jamming delightfully away until the music stopped, replaced with shots. not automatic but just semiautomatic? >> yeah. bang, bang, bang. then again the recharge. >>reload? >> yeah, reload. >> reporter: celia and benjamin were on date night. listening to the eagles of death metal as murderers in the form of three isis suicide attackers emerged from the back. >> we saw blood ever everywhere. people next to us bleeding. so we were all lying on the floor. justrying not to move.. one of them -- so they were mostly i think three of them -- young people, around 20 years old. >> reporter: eight rows from the stage, another group of

20-somethings, hannah and jack. >> jack stepped to the back and looked to the gunman, looked to the front. i could see the lead singer. his face just dropped. >> reporter: they fired as they went. dispassionate. >> they started shooting. shot shot sh shot shot shot shot! that for ten minutes without stopping. >> reporter: some were able to immediately flee to the exit. >> behind the seats. my friend was behind me. and he ducked. and i said, there's a safety exit, let's go. i took my friend's hand. kind of hike -- >> inched your way over? >> yeah. i didn't stay on the floor. stupid of us. could have gotten gunshot, i suppose. >> reporter: celia and benjamin were pinned down, forced to play dead among the dead. >> there was bleeding on my feet- i felt the blood dripping on my feet. there was another one lying on

blood, big blood. >> an ocean of blood. >> reporter: these are the faces of the men and women in that crowd friday night. and in the aftermath, youa picture too grisly to show without blurring it. the attackers i iued no demands but stated their purpose. >> one of the attackers said, you killed our brothers in syria and now we are here. another one said, d d't move orr i kill you, and he started again. >> reporter: those inside desperate to escape. jack and hannah saw an exit. >> just to see people crawling along the floor. >> three layays o o people that froze or tripped and they weren't moving. you had to climb over these people. that was the hardest thing. that you were pushing down on someone's shoulders or standing on someone's back. >> reporter: they spill out of the theater into this back alley. this man hobbling away.

dragging the wounded. and thereen a ledge a woman hanging. she cries out "please, please, mister, i'll pregnant." a grainy figure begins to pull her up as the camera pans away. sebastian is a 34-year-old musician. abc news has learned he saved her but didn't know it until after the shooting. the butchery so savage not even those in it coulul comprehend it. >> i didn't know what was happening. it's only afterwards when we got home in a cab, we sat in front of the tv, we saw the messages that i realized it was an actual terrorisisattack. >> reporter: back insidedeelia and benjamin had lost each other. >> i could see her but i couldn't touch her. i didn't kno if she was hurt or dead. >> reporter: as the gunmen headed towards the stage they cided to make a break for it. >> when we found each other, there was another shooting. so we went back down on the floor.

and then a few seconds afterer that, we heard a policeman near the entrance. and he said, come on, quick, go, hurry up, get out, get out! we were climbing corpses -- >> climbing over corpses to get out? >> yes, yes. >> reporter: they made it out but 89 died in that concert hall. dozens wounded. a country left reeling. minutes earlier gunmenn in a blacac vehicle shot at people sitting outside the terrace of a restaurant. roman lives in the neighborhood which he now calls a cemetery. >> i can tell you a picture thaha is still engraved in my mind, probably forever. the terrace of the restaurant with all the dead corpses that remained there for hours. untouched. no cover, no blanket, nothing. and they were all dead. almost in the position they were when they were having their drinks. >> reporter: romanid all he could to help. >> there was a young girl, 20 or

something. i just stayed beside her because her feet, she had no more shoes. i grabbed a survival blanket and put it back on her feet so she wa not cold. she was dying. >> reporter: 19 people died. nine were injured. >> can you describe the sound of the shots? >> it's like heavy rain on a metal roof. something like t tt. >> that fast? >> really, really, really fast. like really being exterminated. no feelings. no mercy. nothing. it's not human, these people are not human. >> reporter: small wonder parisians are still jittery tonight. yesterday paris's place de republique empty as if someone had pulled a plug. we saw panic from our hotel. >> everybody's running. >> reporter: running for their lives, crouching under restaurant tables, doing

anything to protect themselves. police taking positions, aiming their rifles. it turned out to simply be fireworks. but for those who were actually inin the crosshairs, the bigger questions like, will there be more attacks? will it spread to the u.s.? those will come later. >> in a way you feel so lucmy to be alive. because we don't know how we managed d do this. >> reporter: for "nightline," matt gutman in paris. >> when we come back, stirring symbols of solidarity from every corner of the globe. messages of peace for a woror in mourning. welcome to the most social car we've ever designed. the 2015 nissan murano. recipient of autopacific's

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. imagine. one man's musical message and symbols of peace. the true colors of hope echoing around the globe in a tribute to paris. amidst the horror and grief, a moment of hope. davide martello outside the bataclan theater playing john lennon's "imagine." >> music goes directly into your heart. youu have a mirror in front of you and you're reflecting yourself in this music. >> reporter: after those now-infamous attac the 34-year-old musician drove 400 miles from germany to may at nearly e ery site w wre innocents lost their lives. >> my hope is that all the musicians all around the world are playing music for peace. this is what the world needs right now.

echoeses of support. monuments awash in the colors of the flag. this image trending worldwide. and in paris tonight, a symbol of hope in a city tossed buttot sunk. our thoughts once again but france tonight. thanks for watching abc news. of course we'll stay on top of all the latest developments overnight on our "nightline" facebook page and at abcnews.com. of course tune into gma first thing in the morning for the latest develops. good night, america. it seems today that all you see