I’m really sorry you’re going through this—it sounds like a stressful and upsetting situation. First off, don’t be too hard on yourself. Dogs can develop behavioral issues for a variety of reasons, and it doesn’t necessarily mean you did something wrong.

It’s possible that the experience at the dog park triggered some fear or insecurity in him, but aggression can also stem from things like overexcitement, resource guarding (including guarding you), or even underlying pain or discomfort.

One thing I’d suggest is avoiding physical corrections like grabbing his scruff or pushing him down. For some dogs, that can escalate their stress or make them more reactive. Instead, try redirecting his focus with treats, a firm but calm "no," and giving him space to decompress. https://sprunkiphase5.io

If the aggression continues, a session with a professional trainer or behaviorist could really help get to the root of the issue. You’re clearly invested in making things better, and with the right approach, I’m sure you can work through this. Hang in there!