Is that person a Christian? They described him as a good person. Being a good person is admirable, but it does not make you a Christian.
The most famous Children's song says, Jesus loves the little children (really everybody). Did you hear that? The God of the world loves you and cares about you. What could be more awesome?
The Bible says that all have sinned. This includes good people, bad people, mostly good people, and mostly bad people. It also says that the gift of God is eternal life. It is a gift, that means it cannot be earned.
Jesus, who was perfect, died on the cross to pay for the sins of the world. He was the substitute, or payment for sin.
How do you know if someone is a Christian? The important answer is what did they do with Jesus. Jesus said, I AM the Way, the Truth, and the Life. All other ideas, thoughts, and methods are nice, but they are not the issue.
When you thank Jesus for dying on the cross, and ask Him to forgive your sin, He changes you, and makes you a child of God.
Then you will become a good person, because that is who you want to be. Not because you have to do it.