Great job. You really need to go back, and tell his parents. This is a 14 year old boy, in age only. He is probably proud of his "acting" job crying in front of you. The very same night he probably went back to bothered other girls. Anybody able to do what he did is capable of who knows what else. He is probably making double sure he covers his tracks this time.
Let him get a surprise visit from the police, to they can see what's on his computer. You already did the hard part. Let the police decide whether he deserves another chance. Just think how good he could get in 15 years.Next time it might be your daughter he is blackmailing, and wants nude pictures of.

Frank