The prosecutor can argue that you violated some laws, but they will have to convince a jury beyond a reasonable doubt of that. And they will need a lot more than "I heard the shredder" to convict you. In an overall case, the shredding can be a piece of the puzzle. Shredding, standing alone, is not a crime, nor is shredding as a general matter tampering with evidence.

Yes, if someone wants to bring charges for evidence tampering, they will be required to collect additional evidence to successfully prosecute that crime. That's how it always works. They might collect fragments of the documents themselves, communications regarding the shredding, etc.