dead ball foul or live ball foul

[johnsonboys03]

A1 is oob awaiting the ball to be handed to him for a throw in. While waiting the teams start there inbound play early when B2 runs directly through a screen by A2.
The ball is still dead until the ball is handed to the thrower, correct? There for it would be a Technical foul???
When I first heard this scenario I first was thinking that the ball is at the disposal of the thrower so it would be a live ball common foul, but after researching and studying a little more in depth I believe my initial thought was incorrect.
However depending on the severity of the foul I think I would have just told the players to hold up the play hasn't started yet.
I'm asking two things. 1) what is the correct ruling 2) How would you have handled the situation?