A plane carrying the Chapecoense team, including coach Caio Junior, to Medellin for their Copa Sudamericana final match against Colombian side Atletico Nacional crashed on Monday.
The extent of accident became clear with the confirmed deaths of many of the players and officials of the Brazilian club.
Gabriel worked with Caio Junior when he came through the youth ranks of Brazilian side Vitoria and he broke down as he recalled memories of his friend following Arsenal's League Cup tie against Southampton.
"This is really hard to take. It is something we never imagine will happen with us or a close friend," Gabriel told Arsenal's website.
"I played for Vitoria for five years and I worked with the coach and the backroom staff, and two other players as well. We were very close friends.
"The minimum I can do is send my condolences to all their families and wish that they can carry on.
"I ask for strength for this team that enchanted Brazilian football, a group that five years ago was in the fourth division and surprised everybody.
"We only have good memories to keep in our hearts from this team and the friends I made through football.
"We have a message group from Brazil and I texted them to say "don't leave for tomorrow what you can do for today.
"I say that because on my last birthday I felt this urge to talk to Caio Junior and for some reason I left it for another day and then this tragedy happens."