Tragic news ... Luke Knox, a Florida International University linebacker and brother of Bills star Dawson Knox, has died suddenly at the age of 22.
FIU officials and Buffalo head coach Sean McDermott just confirmed the passing ... though a cause of death was not revealed.
"Our hearts go out to Dawson and his family during this time," McDermott just told reporters at Bills training camp. "We're right there with him and supporting him and his family. Just tragic news that I woke up to this morning.