WHAT?! I can't believe this happened and truly hope you can find these people.

From the sound of your story, it sounds like those three were probably not actually affiliated McDonalds. Were you confident that even Potential Witness 1 was a true employee? Sounds like a scam and heist, but very strange since multiple people involved were wearing (seemingly) legitimate McDonalds clothing. Although, I would note that they were not wearing the uniform that the cashiers were wearing, which may give more weight to the conjecture that they were just lurking in plain site waiting to mug or rip someone off.

I hope you find these guys and they get whats coming to them.