"Steady run of arrests continued Tueday as agents of the federal bureau of Alcohol, Tobacco and Firearms pursued tips and found individuals with illegal rifles..."
Perhaps what they should do would be to give a broadcast radio call for all motorists in the vicinity to reduce speed and bring the area into gridlock to give the police time to set up check points at exit ramps.
This goes against all instincts to "get the hell out", but I'll bet you would get cooperation from enough motorists to create the jam and trap him in traffic.
I'm also concerned that the sniper team/cell is sending observers/spotters in white Astro Vans to draw attention leaving every crime scene but they would be clean if stopped, the sniper getting away in a smaller sedan. Maybe that's why there is so much eye witness confusion.