Ask him what he is trusting in. Is he trusting in Jesus or in himself?
"Never showing any fruit" is hard to say. You say he waas a good man; was there a change when he got saved? Works are not a good barometer, no, but there is a change upon salvation, even if it's just a child who doesn't lie or steal cookies from the cookie jar anymore; and it might be no more than that.
That's because 2 Corinthians 5:17 promises that if anyone is in Christ, he is a new creature. Once they have been saved, Jesus begins a good work in them, as Philippians 1:6 says. But, he lovingly gives us free will, so that person might just be allowed to stop getting better. he may let them become hardened.
But they are still saved. The question to ask is, what are they trusting in? ecause the Spirit int ehm will still testify, even if because of baggage they have tried to block it out.
But, it's possible he just went forward to please soemone, so definitely be talking to him about it.
John 3:16 (KJV) For God so loved the world, that He gave His only begotten Son, that whosoever believeth in Him shall not perish, but have everlasting life.