Complex sentence: Merah boasted to police negotiators on the night of 21 March that he had brought France "to its knees", and said that his only regret was not having been able to kill more people.
Split into simpler sentences: Merah boasted to police negotiators on the night of 21 March that he had brought France "to its knees". He said that his only regret was not having been able to kill more people.