It happened Friday night at a home on David Road in Wendell.
Police say Robert Furey was showing 15-year-old Nick Exley his gun when it went off, killing Exley.
The teen's uncle spoke to ABC11 and said his nephew attended Corinth Holders High School.
"He was a rambunctious, wild young man but very caring young guy at the same time," said the teen's uncle Brad Exley.
Furey is now charged with voluntary manslaughter.