Well, the SWAT tactical gear is not designed for fighting, as far as I know. It's bulky, movement-restricting, it slows the wearer down. Especially an unexperienced wearer like the perp in question. His helmet was too big, most probably limiting his vision, the shoes were ill fitting, bad choice if you plan to fight with someone. This outfit actually causes more problems than that - it catches the attention, so the perp had to take it off before leaving the church, therefore spending more time on or around crime scene. You cannot just roll it into a ball and stuff in a bag, or under the car seat. The helmet, the vest, the protective pads, it all takes space. What if someone noticed it in his car? Risky, if you ask me. Getting rid of it is also not easy, exactly because it's bulky. And hard to destroy, even by fire. Only a juvenile (or someone extremely immature) might think dressing himself in that gear is the best possible way to protect themselves and conceal their identity. If the perp wanted to kill Missy it would be easier to prepare a weapon for that. Ambush her and knock her out with something heavy, shoot her, but getting involved in a fight while wearing this uncomfortable gear?