Frankie Cocozza is reported to be distraught after his best friend Connor Saunders was killed in a fight between two groups of youths.
Three schoolboys are apparently being questioned by police on suspicion of murder following the death of the 19-year-old plasterer from serious head injuries sustained in a fight in the street in Rottingdean, near Brighton.
One of the suspects is thought to be aged just 13.
Former The X Factor contestant Frankie, also 19, cancelled gigs in Scotland and flew home as soon as he heard the tragic news - and has tweeted: "My life will never be the same."
His father Frankie Sr said: "Frankie is absolutely devastated."
Peacehaven and Telscombe FC, where Connor played football and his father was first team coach, issued a statement which read: "It was with incredible sadness we learned that Connor Saunders had died following an attack.
"We have all lost a wonderful person and talented footballer. Connor has many friends because of his lovely nature and his loss is tragic to everyone connected to our club, his friends and family.
"The club is currently in a state of shock. Our condolences go to all the family and we would ask that their privacy be respected at this difficult time.
"RIP Connor, we all loved you and you will never be forgotten."