. >> reporter: burned is exactly what jeweler david margulis got the day architect jason shaw entered his store. >> he was very clean-cut. he was wearing a nice shirt and tie and jacket. >> reporter: like we're dressed? with money in his pocket and engagement on his mind, the ring-shopping romeo puts the staff at ease. >> he then said, "may i compare the two rings and see them both together?" >> reporter: but in an instant, he changes the rules of engagement from a potential suitor to stone-cold crook. >> he turns on his heels and just jumps off the stairway, running out the door. and i took one look, and knew what was going on and ran right after him. >> a crime alert now about a thief dressed so well he took his victims by surprise. >> reporter: tonight, we're taking you inside one of the country's most slick and daring robbery rings. a crew so meticulous, they even had someone wiping prints off of doorkn doorknobs. >> michael young cleaned your fingerprints off the door when you hit it going out. >> yeah. >> reporter: so hardcore they even tased themselves just to see what it felt