No but they do need someone on the inside to open the door...or pass them thru security.
At Domodedovo, there's an area just as you're exiting the international arrivals hall where all of the relatives, hosts, and drivers wait for arriving travelers. It's quite a gauntlet of people you've got to negotiate when you leave. So, it's quite imaginable that this guy could target 100-200 people without entering into the secure area.