Germany Releases Truck Attack SuspectGerman police have released their only suspect from the terrorist attack Monday in which a man drove a large truck through a crowded Berlin Christmas market, killing 12 people. The Chief Federal Prosecutor's Office says it released the man, a Pakistani national, because it did not have enough evidence to charge him with a crime. "The investigation up to now did not yield any urgent suspicion against the accused," the prosecutor's statement read. An unknown terrorist stole the truck and intentionally drove it through a Christmas market outside the landmark Kaiser Wilhelm Memorial Church, German officials said.   The attacker then fled and police captured the Pakistani man about two kilometers away. He denied any involvement in the attack before police released him for lack of evidence. The head of Germany's Federal Criminal Police force said the true terrorist behind the attack could still be at large and said police have not yet found the gun believed to have been used to kill the truck's driver before it was stolen. Chancellor Angela Merkel said it would be "especially hard for us all to bear" if someone who sought protection and asylum was responsible. "This would be especially despicable for the many, many Germans who day in, day out are active working for refugees as well as for those people who actually need our protection and who make an effort to integrate into our country," she said Tuesday. Merkel visited the scene of the attack deliver condolences and drop white roses at a memorial. Merkel said it is important not to let terrorist attacks change the way Germans live.  “Twelve people who were still among us yesterday, who were looking forward to Christmas, who had plans for the holidays, aren't among us anymore,” she said in a nationally televised statement. “A gruesome and ultimately incomprehensible act has robbed them of their lives.” Berlin Senator for the Interior Andreas Geisel announced new security measures to be implemented around the nation’s capital in response to the attack and asked organizers of other Christmas markets to shut down for the day to honor the victims. Witnesses said the popular Christmas market was packed with tourists and locals when the truck, believed to have been traveling in excess of 60 kilometers an hour, slammed into it. Authorities said the vehicle was loaded with steel beams. The White House offered condolences in a statement that condemned the attack. The U.S. State Department had earlier called for caution in market places and other public sites across Europe. A published U.S. travel alert said extremist groups were focusing their attention "on the upcoming holiday season and associated events." It also warned U.S. citizens on the continent to be on the alert for "self-radicalized" extremists, who it said could strike without warning. The Polish owner of the truck, which had Polish license plates, said the vehicle driven by a relative was most likely hijacked after German authorities had him identify the body of his dead employee. "His face was swollen and bloodied. It was really clear that he was fighting for his life," Ariel Zurawski told German broadcaster TVN. Monday's crash bore strong similarities to a truck attack earlier this year in southern France that killed scores of people and wounded many others as France celebrated a national holiday. French police linked that July 14 attack, which killed 86 people and wounded more than 400 others, to a Tunisian national with reputed links to Islamic State extremists. In Photos: