Shallenberger says he made the decision to sack the player the moment he saw it.
“I was at the game and it happened right in front of me. It was shocking – to the point where you wonder if you seen what you seen. It was very shocking,” Shallenberger told The Telegraph.
“On my part it was immediate [to take action]. I’m kind of a hot-head anyway and as soon as it happened I went to the coaches and said he has to be terminated immediately. It would have been within 10 minutes if we didn’t have to follow certain protocol.
“We focus on youth. We have a lot of kids at the game – and that was the most disturbing thing, a cowardly act like that.
“It’s one thing to punch someone in the mouth, it’s another thing to kick someone in the back. It’s cowardly – and it’s not Pittsburgh.
“I did not speak to the player personally – the coaches handled it. He won’t play for Pittsburgh again – I can tell you that.