Well it'd all be news. Here's the steps: 1) Fed makes announcement (news generated) 2) Machine traders read news and make appropriate trades 3) Markets move

Well it'd all be news. Here's the steps: 1) Fed makes announcement (news generated) 2) Machine traders read news and make appropriate trades 3) Markets move (if big enough, news generated) 4) Machine traders see markets move, possibly make appropriate trades 5) Markets move again (if big enough, news generated Each movement in the markets, if it were big enough to be news worthy, would generate a news event. That is ok, because news readers would want to know about large market movements (well other news readers would - I really wouldn't). It's up to the traders to decide if they want to keep buying/selling.