I can't see how a starter gun is going to cause a panic leading to crushing/trampling of masses, or anything remotely close to those kinds of consequences.

During daytime hours it's usually pretty legal to make all kinds of sounds.

If someone wants to nitpick the "gun" here, just rig an internal combustion engine that backfires as loud as a gun, or literally put in a speaker / horn that can produce the same sound.

There's ways around all the little "but what about" in this scenario.