West Ham owners David Gold and David Sullivan were forced to leave their seats for their own safety after being confronted by angry fans on an afternoon of shame at the London Stadium.
Some supporters invaded the pitch while hundreds of others congregated beneath the directors' box to protest against the club's board as the Hammers slumped to a 3-0 defeat to Burnley.
Some fans even made a throat-slitting gesture while missiles were seen to be thrown in the direction of the executive seats.
Down 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.
The Burnley coaching staff even had to let children sit on their substitutes' bench to avoid being caught in skirmishes in the stands.
Police said there were four separate pitch invasions and received two allegations of assault which they said are being investigated.
West Ham said an emergency meeting had been called with all London Stadium stakeholders, which includes Gold and Sullivan, whose decision to uproot the club from Upton Park to Stratford has caused resentment.
The Football Association is also set to launch a probe, with a spokesman saying: "The FA strongly condemns the crowd disturbances seen today at West Ham United versus Burnley and will be seeking observations from West Ham as well as awaiting the match referee's report."
A Premier League statement added: "It is essential that everybody who plays or attends a Premier League football match can do so safely.
"There is no place at any level of the game for what happened at the London Stadium today. While the official investigation of the incidents will be carried out by the Football Association, we will be asking our own questions of West Ham United about what happened this afternoon, especially to ensure similar events never reoccur.
"We would like to commend referee Lee Mason and his team of officials for their actions which, combined with the cooperation of players and coaching staff from both clubs, enabled the match to be completed."
West Ham manager David Moyes condemned the scenes. He said: "As a supporter you can't cross the line. You can't come on the pitch. That's the rule.
"What we need is the club, supporters, players, everyone, is to pull together. "
It was an horrific end to a turbulent week which saw a protest march called off as fans' groups turned on each other.
A smattering of supporters had trooped along the proposed protest route regardless, but in the stadium the mood seemed more apathy than antipathy.
There was even a minutes' applause in memory of the 25th anniversary of the death of Bobby Moore, with a mosaic in the crowd bearing the great man's name and shirt number.
But once Burnley took the lead through Barnes early in the second half the atmosphere immediately turned toxic with four separate fans running onto the pitch.
When Chris Wood scored the second goal hundreds of fans poured along the concourse between the tiers of the stadium they resent so much to confront Gold, Sullivan and vice-chair Karren Brady, while another supporter grabbed a corner flag and stuck it in the centre circle.
Wood hit a third late on but hardly anyone was watching the match at this stage as the shocking scenes completely overshadowed Burnley's victory.
Manager Sean Dyche admitted: "When we scored the second the atmosphere changed.
"We know people can't come on the pitch but I can't imagine it was dangerous for the players.
"It's a tough situation for a player, no one wants to see it. But they get frustrated, they are just saying, 'Get off the pitch'.
"Hopefully there are better times ahead for West Ham."