It's an interesting train of thoughts.

Investigators would need to connect the dots. If they weren't able to connect them, it would look like a normal accident, which happens all day. So why would an agent call gigworker1 to that place in the first place? And why would the agent feel the need to kill gigworker1? What could be the reasoning?

Edit: I thought about that. Gigworker 3 would be charged. You should not throw rocks from a bridge, if there are people standing under it.