SBM
She could have been shot in the face or back of the head. But just because the guy who helped them didn’t mention defensive wounds doesn't mean they weren’t there or maybe not significant. It’s also possible Chynna tried to defend herself after seeing Lucas shot but was overpowered quickly. If so I can see them wanting to “punish” her even more. Of course, JMO... speculating here along with everyone else since facts are so skimpy.
She could have been punched and kicked in the face, a rock slammed into her, run over by either vehicle numerous times, any and all and every possibility that resulted in a brutal death, which was not a quick death, as has been discussed before, in regard to the statement by the person who discovered the body . .. It took a very long time to identify Miss Deese.
Shooting would have been only one method. Because of the short duration of their program, I figure lack of ammo had a lot to do with the number of victims, and their victims manner of death. The guns may have been used to threaten and over power their victims, but it isn't definite that all were shot.
By the time they got to Prof.Dyck they would have discussed it over and over again, what they did, what they did right, what they did wrong, how they could improve, what to expect, how to achieve a result with perhaps less, or , perhaps more violence, who does what best, who did this bit better, who should have a turn at this aspect of murder, who . .. and so on, perhaps watching video's of themselves to work out a more efficient process. .
Certainly, murdering Miss Deese and Mr Fowler did not steer them in any way into another path of achieving a bit of a rush, or getting further into Canada.. Murdering people seemed to have , after the reality as opposed to the fantasy, an attraction and not a repulsion.
It seemed to have encouraged them in their endeavors to get another notch on their belts.