The 29-year-old American was on the ice for Nottingham Panthers when a skate slashed his neck in the Challenge Cup game against Sheffield Steelers on Saturday night.

The 8,000-strong crowd in the Utilita Arena in South Yorkshire were asked to leave, and Johnson was later declared dead by paramedics.

Posting a picture of the player on Instagram, his fiancee Ryan Wolfe also wrote: "My sweet, sweet angel. I'll miss you forever and love you always".

It is widely reported the pair became engaged over the summer.

The Sun reported Ms Wolfe ran onto the ice in Sheffield after the incident, as players formed a protective ring around Johnson, shielding him from the crowd.

South Yorkshire Police are also now investigating the incident, with a spokesperson saying: "Officers attended the scene alongside other emergency services and one man, aged in his 20s, was taken to hospital with serious injuries.

"Sadly, he was later pronounced deceased at hospital. Our officers remain at the scene carrying out inquiries and our investigation into the circumstances surrounding the incident remain ongoing.

"We would encourage the public to avoid speculation regarding the incident while we continue our inquiries."

Fans leave tributes

Fans and players left tributes at Nottingham Panthers' Motorpoint Arena on Sunday, after news emerged of Johnson's death.

Flowers were laid at the venue, with those there expressing condolences over the incident.

One message left said: "Our hearts are breaking, you will be forever missed and forever in our hearts."

There were also tributes left from Glasgow fans, whose team was due to play Nottingham on Tuesday. The match has been postponed.

Speaking to the hundreds of people who had turned up in Nottingham, assistant coach of the Panthers, Kevin Moore, said: "We really appreciate all of the support and tears and love.

"Our hearts break with all of yours. We are grieving this together as a team, as a community, as a city, and we're going to get through this together with a lot of love, a lot of thought and a lot of laughter."

'It's like a bad dream'

A witness at the arena called Hazel told The Sun newspaper she could not get what happened "out of my head".

She said: "It is like a bad dream I can't wake up from.

"Suddenly during the match, the blade struck the player's throat and there was blood everywhere. He tried to get to the side of the arena but came crashing down.

"His teammates looked horrified and banded together around him to shield him from the crowd. They were amazing.

"We were all praying and hoping he would make it, but sadly he didn't. Our hearts go out to his family and friends and teammates

"I cannot imagine how they are feeling. We are feeling absolutely numb ourselves. It was a freak accident, totally tragic, and no one was to blame."

Before joining Nottingham Panthers, the Minnesota-born Johnson played in Pennsylvania for the Pittsburgh Penguins, and Sweden for the Malmo Redhawks.

He also played in California for Ontario Reign, who have since paid tribute to their former player, and in Germany for Augsburger Panther.

'Forever in our hearts'

After Johnson's tragic incident, Ontario Reign made a moving tribute before the club's American Hockey League game against the Abbotsford Canucks on Sunday.

Johnson's name was announced to the crowd as his number 49 jersey was placed on a chair in the middle of the ice by former Nottingham player Jacob Doty.

Every Ontario player touched the jersey in a moving gesture, with a video of the gesture posted on their social media accounts with the caption "forever in our hearts".