stills from an uncompressed video are that clear
All video is compressed, it’s just a question of how much. That said, they released the video, someone linked it, it is remarkably clear, so I concede that he did have a knife. However, it doesn’t look like he “charged at the cops” with it, rather he was running away, but didn’t realize one of the cops had gotten on the other side of him. You can really see his oh shit moment when he realizes the person he’s running toward is another cop, and he stops, but they’re already shooting him (and each other, and several passengers) by then. What was the rush? The train wasn’t going anywhere.
Years ago, I read the book Empire because I had been a fan of OSC and didn’t know yet what a dickhead he was. The book describes more or less exactly what you said, it was comical, but also kind of sad.