I'll give you that that Bellingcat stuff makes it look like it wasn't Erdogan arranged. It doesn't seem terribly Gulenist either. Seems quite possible it was secular / nationalist army types similar to Turkey's previous coups. Erdogan was obviously out to get Gulenists before the coup as he must have had the list of judges to fire prepared before hand so it's quite likely that he's taking the opportunity to have a go at them regardless of evidence one way or the other.
Though it wouldn't surprise me if Erdogan had one or two people try to stir things a bit like the Syria false flag idea (http://www.zerohedge.com/news/2014-03-27/here-youtube-false-...)