I would read the two books suggested by Grizzled Bear...they are worth it to prepare yourself to continue the conversation with this young man. I would also suggest reading “The Lie” by Ken Ham and “The Battle for Truth” by David A. Noebel. “The Battle For Truth” states in the introduction “That's what this book is all about-helping to recognize the source of some of the most influential, yet damaging ideas and values of our culture and understand the unbiblical (and unrealistic)assumptions about reality from which they arise.”
Prepare yourself to continue the conversation and pray that God would create the circumstances so that the conversation will continue. I will be in pray for you and this young man.
God bless