As deadratdeadrat says, without more context it's hard to comment clearly.
Nonetheless, your first version sounds wrong in part because it's ambiguous. The first four words are a principal clause by themselves, but an ungrammatical one (concern is a noun and something acting as an adjective is needed — concerned, perhaps). Thus the first four words misdirect the reader to expect a different construction than you go on to deliver.
The focus of your thought in the sentence is he, not they. So you confuse things by starting as you do. I would use the grammar to reinforce the thought by making the same point but beginning the sentence with he.