they could have surveillance cam footage to work with or audio sensors to triangulate where shots came from. but along a stretch of highway there are also disadvantages. in areas like this, what are investigators up against? >> it's very tough in an area alongside of a major highway like i-10. you have areas like this over here, kind of a junkyard with ramps crossing over. i-10 is very similar to this type of makeup. you've got wooded areas. you have fields. you have industrial parks. you effect an area like this, there's not going to be a lot of people around, nobody's going to hear or see what's going on. >> arizona's public safety director says they're looking for the public's help in this case. art roderick says information from the public is going to be crucial and he says police may have already gotten critical information, maybe that they're holding back so that they don't tip up possible suspects including maybe an area they want to surveil. >> does the time frame of some of these incidents come into play? >> it very well could. most of these incidents have