[Route66]

Perhaps the Michael's choice has some significance, but they also targeted several gas stations. Could be they just discovered that these locations provide easy targets and favorable physical layouts for their attacks.

[Dog]

I will bet the rent ......that all the shooting sites are near a major highway.....for easy bugging out.

[browardchad]

Could be they just discovered that these locations provide easy targets and favorable physical layouts for their attacks.

Very possible; I also wonder if the first hit (at Michael's in MD) wasn't simply a miss, and another Michael's was visited for that reason. That would imply some vanity on the part of the shooter.