backcourt violation/ ball oob where?

[number 26]

hello
quick, easy one
happened in my team's game yesterday
ball in front court.
pass from a1 to a2, from the corner to up by the free throw line, is thrown over his head, with no one else touching it.
ball bounces into back court. a2 chases.
question concerns ball oob to team b.
where is the ball placed if:
a) a2 catches up to the ball in his back court, just before it was to go out of bounds, under his basket.
or b) a2 decides not to grab the ball at that point and it bounces oob, untouched.
as always, thanks.