The boy, named as Daniel in tributes, died on Saturday evening, nearly a week after he touched overhead powerlines on the railway bridge in Milton, north Glasgow.
The 12-year-old, who was with a pal at the time the accident happened on Sunday, August 18, was rushed to hospital in a life-threatening condition, receiving specialist treatment.
But he could not be saved, and floral tributes were left at the scene of the tragedy, along with a Celtic shirt with the letters 'GBNF' written across it.
Bouquets of flowers stretched along the railway bridge where the tragedy happened.
"Look after us down here."
Two notes pinned to the same bouquet said: "You were one of my best friends and I can't believe you are gone.
"I will always remember you.
"You will forever be in our hearts; such a kind, caring, funny and generous boy.
"You will be sorely missed, pal."
An envelope attached to another bunch of flowers said 'Rest In Peace Daniel'.
One heartbreaking note, written in blue pen, said: "RIP. You are my best friend and I will miss you forever. Love, Marty."
Another described the 12-year-old as like a 'big brother'.
Linda Cruickshanks, whose son was with Daniel at the time of the accident, said: "We are going through bereavement ourselves.
"For now I think it's best both families are left alone.
"I know everyone means well but this is not the time."
SNP MSP Bob Doris said: "I want to offer my personal condolences for their sad loss.
"I have since been in correspondence with Network Rail to seek reassurances that the safety of the track and power lines will be urgently reviewed.
"A thorough investigation must now surely follow.
"For now my thoughts are with the child's family and friends."
Inspector Alasdair McWhirter, from British Transport Police, said: "This is a truly tragic incident, and our thoughts and deepest condolences are with the boy's family and friends.
"We have specially trained officers supporting his family during this incredibly difficult time and I would ask that their privacy is please respected while they come to terms with their loss.
"We have no reason to believe there were any suspicious circumstances to this incident and we will be preparing a report for the Procurator Fiscal."