The 29-year-old American reportedly suffered a slashed neck during the second period of the game at Sheffield’s Utilita Arena.
Eight thousand fans were evacuated from the arena.
Nottingham confirmed in a statement on Sunday morning: “The Nottingham Panthers are truly devastated to announce that Adam Johnson has tragically passed away following a freak accident at the game in Sheffield last night.
“The Panthers would like to send our thoughts and condolences to Adam’s family, his partner, and all his friends at this extremely difficult time.”
Dave Simms, Steelers’ long-time general manager, added his voice to the long list of tributes to the former Pittsburgh Penquins NHL player.
Simms said: "Just a horrible night at the arena, tragic, our thoughts go to Adam's family, friends and team-mates, nothing can prepare you for something like this.
"To Steelers fans, we will do everything we can to ensure the team are looked after in the best possible way.
"Seeing the players, staff and medical staff from both clubs last night all working together as one was something I will never forget, the effort they all made was outstanding."
Sunday’s three Elite League games in Belfast, Fife and Guildford were postponed following Johnson’s death, while Nottingham later confirmed via X, formerly Twitter, that Tuesday’s home contest against the Glasgow Clan had also been postponed.
Minnesota-born Johnson played for Pittsburgh Penguins in the National Hockey League before spending the 2020-21 season in Sweden with the Malmo Redhawks.
Johnson went on to play in the American Hockey League for the Ontario Reign and in Germany for the Augsburger Panther before agreeing to join Nottingham for the 2023-24 campaign.
Full coverage in news, pages 1 and 2.