Extremely emotional moment at Cowboys camp Thursday ... head coach Jason Garrett fought back tears during his meeting with the media after learning of his friend's son's death.
Luke Laufenberg - the 21-year-old son of ex-Cowboys QB Babe Laufenberg -- was diagnosed with Leukemia back in 2017 ... and he died Thursday after a 2-year-long battle with the disease.
Garrett addressed reporters shortly after learning the news ... and the scene was tough to watch.
Garrett was extremely emotional in trying to describe Laufenburg's son, saying, "You guys have heard me talk about fight a lot.