Sources say Trump's golf outing was LAST MINUTE DECISION, so how did the shooter know?

CNN posted this headline "Trump's golf outing was last-minute decision, sources say." That was followed by the text "Former President Donald Trump’s golf game on Sunday was a last-minute addition to his schedule, two sources familiar with the matter said. Trump had no public events on his schedule for Sunday." Source

Now people are asking "how did the shooter know Trump would be there?"