I might disagree with a few earlier posters about the knowledge (significance/timing) of that Monday February 13th being a day off school due to previously unused snow days. The Delphi Middle School dismissal time is 3:15PM
http://ms.delphi.k12.in.us/UserFiles/Servers/Server_392081/File/BELL SCHEDULE1.pdf which means the earliest a perp might normally expect to find teen girls on the bridge, absent knowledge of the day off, would be 3:45-ish depending on busing, distance to abduction point, etc, not as early as 2:07 when the snapchat photo was taken (and they could've been spotted even an hour earlier) I'd lean against anyone planning out in advance an attack of this sort on a Monday in February if they were not expecting to find victims near the bridge until 3:45 and knowing it began getting dark by 6:20 -- that's a fairly tight window, especially considering the following Monday was Presidents Day, a more universal school day off where greater opportunity might've existed. Of course it's possible it wasn't all that far pre-planned/scoped out and BG read about the day-off in a morning newspaper or heard discussion that AM in the local coffee shop.
Another point of somewhat disagreement - the oft-pointed out "mild" day. While yes slightly above average temperature-wise, the Delphi high on Feb 13 was just 43 degrees with the low at 27.
http://www.accuweather.com/en/us/delphi-in/46923/february-weather/332895 The historical averages as attached are 38 & 20 so yes a bit warmer, especially the sun might've made it feel warmer, but not crazy warm. In hindsight, I think commenting locals are mistakenly remembering the 8-day stretch Feb 17-24 where the temps exceeded 60 every day (and the previous Sat Feb 11th was also a warm day), but not so much so on that fateful Monday. Given later-afternoon temps likely dipped below 40 on 2/13, many of us older generation would prob feel BG was not as overdressed as the girls may have been underdressed (tho we adults know how that often is with kids)