Lightning Rounds

Lightning Rounds deals 2 damage divided as you choose among one or two targets.
Whenever a vehicle you control attacks, if
Lightning Rounds is in your graveyard, you may
pay {2}{r}{r}. If you do, you may cast it without
paying its mana cost.
"Several direct hits, commander."
"I'm not seeing anything. Duds?"
"No, sir. Give it a mo—