Unsporting T at end of 1st half.

[Fiji07]

Had this in my game tonight and not sure we handled it correctly.

End of 2nd quarter A1 shoots misses and A2 rebounds and scores as time expires. Basket counted good. As ball comes through the net B1 spikes it volleyball style into the ground and it bounces hard off the ground and bounces into the bottom of the backboard. I'm L table side and call the unsporting T on B1. We administer the 2 free throws prior to the teams heading to the locker room and start the 2nd half with alternating possession. The possession arrow was toward A so either way they were going to start the half with the ball.

Should the throw-in have been an alternating possession throw-in or as a penalty from the T?

Please give a rule reference if you have it.

Thanks.