To me there is a cascading blame chain.

#1 is the "Air Boss" for deciding it was fine to have models and full size operating simultaneously.

#2 is the RC pilot for not saying "What!! Are you crazy?!" And then for not realizing HE was crazy for not landing after the first pass.

#3 (distant) is the bipe pilot who perhaps should have seen the RC plane on his first pass (it was reportedly in the air) and for not yelling "LAND that plane NOW!!"

Bad decisions lead to bad consequences every time!!