and they would come up and they would put their finger close to, point out the image of rembrandt. and if they got too close, then the alarm would sound. >> reporter: like the motion detectors, this alarm was not connected to the outside world. but did the thieves know that as well? because they didn't pack up and leave at that point. they continued on with their crime. and they took their time. >> same path backwards. goes through the early italian room, the rafael room, all the while passing incredibly priceless art. famous art. rafaels, important chinese pieces, an gelco. and walked back through to the short gallery, where the thief takes five sketches by de ga and a napoleonic the first regiment carried. throughout his actions, he's