So sorry - what a dreadful thing to happen. Nothing will bring your sheep back, but perhaps this young man will have learnt a valuable lesson when driving on country lanes.
I have to ride and drive our ponies along a single track country lane, and it is used by boy racers, who come round the corners at an alarming speed. I hate being on the lane, but have no choice.
I have noticed a lot of dairy farms have flashing lights, similar to traffic lights, they can activate when moving their cows. And one farmer has to cross a main road with his herd, and usually has a couple of men with him, standing in the road, holding the traffic back on both sides. But, in a way, they are risking their lives, as some drivers try and dodge round them!!