Former West Ham midfielder Frank Lampard described the atmosphere at the London Stadium as "toxic" after angry protests marred his old club's Premier League defeat to Burnley.
There were pitch invasions by some supporters while hundreds of others gathered beneath the directors' box to protest against the club's board as the relegation-threatened Hammers crashed to a 3-0 loss.
Some fans even made a throat-slitting gesture while missiles were seen to be thrown in the direction of the executive seats.
On the pitch, West Ham captain Mark Noble grappled one fan to the floor, defender James Collins frogmarched two away and Burnley forward Ashley Barnes tripped another over.
And Lampard, who left West Ham in 2001 to join London rivals Chelsea, hit out at the way the supporters vented their frustrations.
"It was very toxic. It was a horrible feeling in the second half, in particular," the ex-England international said on Match of the Day.
"Fans coming on to the pitch, I understand Mark Noble's position. He is Mr West Ham and doesn't do this for the fun of it.
"He cares and that is why he reacted in that way. This wasn't right. This was very aggressive today."
Lampard had some sympathy for the fans, but did not condone their actions.
"I understand some of the fans' feelings in general," he added.
"They move stadium, feeling like they have lost some of their identity moving stadium, with part of the deal to move stadium and fight for Europe and invest.
"The club have a £29million net spend since they have moved, which is not really enough, so they have gone backwards.
"The fans are asking questions, but the way to ask a question is not a demonstration mid-game as that affects the players."
It is not the first time that there has been unrest at West Ham's home matches this season, but Jermaine Jenas says Saturday's was the worse he has seen.
The former Tottenham and Newcastle midfielder said on MOTD: "Today was the worst. I've been down to a few games this season at London Stadium where it's also happened.
"I remember Brighton at home when they got beat heavily. There was fights breaking out in the stadium then.
"I do feel for the players. Don't get me wrong, they are under-performing but playing under that type of pressure on top of being in a relegation battle, it just doesn't help."
Saturday's loss was a fourth defeat in five Premier League games for the Hammers and left David Moyes' side 16th in the table, three points above the relegation zone.