Everything that we’ve seen for this beta tester is honestly making it seem like Nathan is the perpetrator.
1. He’s a medical professional
2. He could be looking into how to change betas into omegas bc he wanted to transform himself into an omega
3. He has a silver car (I don’t remember the model they said but it’s interesting that the car color is the same)
I could be wrong tho. David might be making a reappearance later in the story as the main villain who knows lol