This would pretty much depend on how ‘reliable’ this tip was in order to stop all those cars. If it was an eyewitness that would be enough, but an eyewitness should be able to provide SOME physical script of the perp. Weird scenario.
Perhaps a tracking device in the loot?
Not enough tracking resolution to the exact car, but good enough to get to the intersection...
That would probably stand up in court, if it was the case. People around here are bashing the tactics, but what's more important: a short detainment of innocent individuals, or catching a violent criminal?
Would you give up 10 minutes of freedom in order to get this guy off the street?