Reading this, I'd speculate that the local reporter got the tip from somebody in the FBI, who was aware of Clinton's security, timing and other plans.
Also notable, this report claims (with substantial supporting assertions) that Lynch was not expecting the meeting. Other reports claim she was rattled afterward.
This meeting was supposed to be forever hidden from the public. Clinton Crime Family.
Here you have Bill Clinton, seeking what seems to be an emergency face-to-face with Lynch. Risky.
We learned from Strzok and Page that Lynch knew well in advance that Hillary was going to be cleared of any charges. I would have to think that any promises or deals that Hillary made with Lynch would have been privately made months before.
Then why the tarmac meeting?
Something went wrong.