Interesting sentence. You can die watching a gate (for a loved one to appear) or you can die watching over a gate (leaning on it and looking up and down the road. However, to "oversee" in English means to monitor how something is done, therefore "overseeing the gate" would be the very strange sentence that he died watching the gate being made. Does anyone know exactly what "supraveghind" means in Romanian?
I interpreted it as he was the commander of the gate, it was attacked, and he died in command.
Or he was supervising the guard at the gate and just had a heart attack.