Thunder bolts of various designs are pretty common military symbolism, even in the US.

The version they used is readily available in unicode fonts ⚡︎

So is a closer equivalent to sig rune ϟ

So to your point, they may have chosen the close enough symbol.

My point is, their actions are plenty to judge them as the militarized police of an authoritarian administration. We don’t need to grasp at straws to prove this.