I would urge caution Bille until someone with strong French reading skills confirms things. I've been misled before by computer translations. I get the impression from the accounts that the original "hit an run" version may have been printed in error by the reporter. Again, I would wait for this to be confirmed. Hope it is true however and again, my sympathies to all involved in this sad accident.
My main language being french,
They said that the kitesurfer reported himselft to the police station where he was questioned. He told the police that he didn't think that the accident had been so severe. He even helped afterward until the medics arrived.
So yes he was suspected of hit and run but he reported to the police station where he was release after that they concluded it was an accident.