Though if we’re being honest here, Canadians make the most sense. The memorial service takes place with dozens of protesters in the background. It makes sense for one of them to have a gun that they shoot during the outdoor service. Gilead soldiers act in a much different way.
June would also be made a martyr to resisters in Gilead if she were killed by guardians. It’s not necessarily in the best interest of commanders for June to be killed now, with tensions at an all-time high.
Source: https://www.distractify.com/p/who-shot-at-june-the-handmaids-tale