Could be related events, but we need more info.
Same with Hamza/Saudi national. He could be Hamza, but we need more info.
We may need more info, if facial recognition is not enough. But the folks at the CIA and DHS (I don’t know who created that “known terrorist” file...) more than likely have a DNA result. Is that enough information?
They apparently believe the evidence of him being a terrorist is certain enough to stake a 20-year prison sentence on it. I’d say that’s pretty confident.