What if it's several or many needles in a haystack? This seems less and less a lone nutcase sniper driving around in a white van. What if it's a terrorist group using several snipers and drivers and vehicles? And who've planned it out well enough that they have garages and places to park the vehicles which may have been seen and get into another waiting car?
Well, then it is gonna be harder to catch them isn't it? Or not... If there are many, then there are also more wives/girlfriends/relatives/friends who may make a phone call.