If the culprit hasn't been discovered yet, I'm gunna take a wild guess, because that is the EXACT same damage I have on mine. My nut came loose on my UCA allowing the UCA to move back and forth. The UCA jammed itself through the shock tower pretty much. That looks EXACTLY what mine looks like, and I found it with the UCA still rubbing against it, with the nut loosened, so I know that's what caused it.
Yep, it is from the upper control arm. I would also say, hammer her down weld her up, but also re-enforce it like 12sec67 did. I did the same thing. I also added a few smaller pieces on the inside to help it from cracking.