this morning, new york city on high alert. 1,000 additional law enforcement personnel deployed across the region. citizens urged to stay vigilant. counterterrorism officers, state and local police, and the national guard patrolling major transit hubs. >> we'll be doing enhanced bag checks. throughout the city. >> reporter: saturday night's blast caught on this surveillance video circulating online. sending pedestrians running and ducking for cover. >> a bomb just went off in new york. >> reporter: the 23rd street location, a bustling center of restaurants and night life. this surveillance video from a fitness club across the street, capturing the chaos. watch again as the force of the blast rocks the camera. >> there was big black clouds of like smoke. >> all of a sudden, we hear, boom! [ explosion ] >> reporter: so strong, it blew out windows of adjacent buildings and cars, sending shrapnel and glass flying. this woman bloodied and dazed. helped by a bystander. >> come with me. i'm...