He hasn't tweeted all day. There is no way this is a hoax. If it was, he would be tweeting up a storm.
This seems to be escalating way faster then I expected. It hasn't even been a full day yet, and he is on his way to Walter Reed. Now, we can say "Precautionary measures", but all President's hide the severity of their medical issues like crazy. Reagan even faked like a bullet didn't face him, and he was in constant pain even before someone shot him. So to announce the President is being taken to Walter Reed at this point... yeah, this isn't nothing. Trump's administration is incompetent at a lot of things, but they understand the optics of not looking weak.