This might be a pretty obvious question, but can a unit inside a transport fire at a different target than the transport. This came up in a game against my buddies guardsmen when his chimera gunned down a tactical squad in front of it and then his plasma vets that were riding inside decided to take potshots at my assault squad that was ready to charge their ride's flank. Is this legal or do they have to fire at the same target? I don't think there's anything that says you can't as transports and their passengers are technically separate units but I kind of hope I'm missing something. This seems a little bit broken to me...
Also, can someone explain the penalties that come with shooting from a transport that has moved at different speeds? I know that if it moved 6" the models inside count as having moved for the purposes of firing rapid fire and heavy weapons, but is this still true for when it moves 12", or even 18" in the case of fast transports? And do the weapons being fired by the passengers count towards the number of weapons the vehicle is allowed to fire (i.e. everything while its stationary, 1 after it moves 6", etc.)?
Thanks for the help. Our local guardsmen player is starting to be a real

with his constant rules lawyering and big ego. We've been trying to find a way to turn it around on him for the longest time...