I doubt a Swedish Pressbyan (it looks like the one in Central Station) has protective glass shielding the clerk, and the brief snatches of her behind seem to confirm this. It's not a locking door trap - which is why the guys are needed to keep it closed. It's almost unheard of to have that kind of protection in anything other than petrol stations, bookeeper's (betting shop) or off-licences (liquor stores). The most likely explanations include, in his urgency to get out, he didn't consider it. Or he just wanted money, and didn't actually want to commit violence. Or he knew that taking a hostage would result in a much more serious criminal penalty. Given its a train station, there is almost certainly police nearby and the incident is probably being observed on CCTV by at least transport security - so he didn't have a lot of time to get control of a hostage, convince the people blocking the door he would hurt her if they didn't open the door and then to make a getaway.