Fighting broke out amongst Millwall fans towards the end of their 2-0 FA Cup semi-final loss to Wigan at Wembley on Saturday.
Police with batons moved in to quell the trouble in an eerie reminder of the scourge of hooliganism that once plagued the English game.
The trouble, which left many young children in the stands in tears, came on the weekend of the 24th anniversary of the Hillsborough disaster.
One Millwall fan was spotted on TV, snatching a police officer's helmet and smilingly tucking it inside his jacket.
"I didn't see it. I need all the facts and information before I form an opinion,'' said Millwall manager Kenny Jackett.