The movie focused so much on the falling and him looking at the picture but then you know it reminded us that this was in 2001. We don't know that that was his dad it was alluded to but it was also shown that when when mom was talking to him at that exact time they showed that's when the building film we knew he was there on the phone. The poignancy of like the falling man and even the pop-up book he makes for his mom at the end of kind of the man going backwards up into the building hole is him trying to find something physical that he can grab onto It's almost nearly as if  he's feeling either from shame or just grief