Transcript for Berlin Terror Suspect Was Known to US Agencies

Turning out to the all out manhunt across Europe for the prime suspect in that devastating terror attack in Berlin had desperate search is on for this man it's 24 year old niece and the air. From the North African country of Tunisia and we now know he's no stranger to German authorities. Here's a look at the popular Christmas market where the truck barreled through its been scrubbed clean. And is set to reopen today and US law enforcement officials have issued a bulletin worried about a similar attack. Here at home at one of the most crowded events of the year in she's Maggie relief with the details. Overnight rare search across Europe for this man 24 year old on his armory of Tunisia. Germany warned he could be armed and dangerous. According to a German lawmaker armories wallet and ID were found in the battered semi truck after a bulldozed through this crowded early Christmas market. Crushing stalls killing eleven and injuring dozens more. Now police searching what they believed to be his home as German terror officials have had their eye an armory since he came to the country Seeking Asylum in Tony fifteen. It was denied over concerns about his ties to radical Islamist and allegations of petty crimes. Germany then tried to deport him but he didn't have the paperwork to prove he was Tunisian and so he stayed. No ruthless. Funding to the tragedy by opening up the city's famed Christmas markets once again. ABC's not gotten it is there people have been going out to that he had been urged to get back to normal by the government here. But they've opened under heavy security we've seen barriers concrete barriers go up and a lot of those markets and a lot more police presence. The attacks also reminding Americans to be on alert. Federal and local law enforcement authorities have issued an urgent bulletin amid growing concerns that a similar attack could happen here on US soil. Warning specifically that time square is annual New Year's Eve celebration could be a target. Saying that while there is no specific threat we remain concerned about unaffiliated lone offenders and homegrown violent extremists target in the event. Now he really ABC news Washington. And also there in Germany did Chancellor Angela Merkel is facing growing criticism for allowing nearly a million migrants to enter that country. Here at home president elect Donald Trump condemned the attack and he appeared to suggest. He may go forward with the Muslim ban he proposed during the campaign. Plants you. Trump had a adjusted his pledge on a Muslim bad during the general election to say he would focus on stopping immigration from certain countries. With ties to terrorism.

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