Football fan? (I'm more than half serious -- I think it's some domestic nutjob.)
Evading detection in a suburban setting involves, in my opinion, strategy and planning. As in: only strike when there are a lot of people moving around.
The movement provides cover for the shooter to become active and then get away in the seconds after activation.
My belief is that most people, when looking for someone like a shooter, will tend to use pattern recognition rules in a negative manner. That is, anything that breaks the pattern will generate suspicion, especially in an alarm situation such as just after a shot is heard. By pattern recognition I mean informally the kind of stuff the brain and eye use to figure out numbers in charts used to detect color blindness.
Patterns include sex, gender, dress, vehicle type and color, speed, and so on.
Patterns of normal weekend activity differ significantly in my opinion from patterns of weekday workday activity. The weekend patterns in my opinion make it somewhat more difficult to blend in than the weekday patterns. Also the densities may be different-- on the weekends it can vary significantly, usually lower except near a public event such as a concert or sports game. Also, people are able to devote more attention on weekends to being careful than they are on their way to work during a normal commute day.
If the shooter(s) do not want to get caught it will be difficult to catch them since suburban and urban settings provide almost ideal getaways for a sniper-- highways and cars. The authorities in my opinion are not utilizing the public to the maximum for detection. More profiling information should be given. People could then let it become part of their pattern recognition violation consciousness. The authorities need all the help they can get to catch these shooters and instead the media have been let loose to warn people to be on the lookout for gun enthusiasts who happen to have AR-15s or subscribe to Guns and Ammo. That probably won't result in catching the shooters because if nothing else they have already demonstrated they are competent in blending into the existing population.
Also I don't think the shooters have regular workday jobs and live in the area. Anyone having normal workday jobs and living in the area will come naturally under suspicion from his/her neighbors, work colleagues, etc due to their lack of alibi for the time periods in which the shootings occurred. A local who made known his/her interest in guns (religious sect, etc.) would fall under correspondingly more suspicion.