WEST HAM fans were filmed walking out against Arsenal after just 34 minutes before their team launched a short-lived fightback.
The Hammers were left stunned as Mikel Arteta's visitors raced into a 4-0 lead in east London.
Gabriel Magalhaes, Leandro Trossard, Martin Odegaard and Kai Havertz were all on target for the Gunners.
West Ham were second-best all over the pitch as they failed to record even just one shot in reply.
And video footage showed numerous supporters leaving their seats inside the London Stadium.
Some were seen calling time on the first half in the 34th minute.
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And the exodus only grew when Arsenal bagged their fourth soon after.
But those who made for an early exit missed West Ham net a quickfire double to make it 4-2.
In the 38th minute, Aaron Wan-Bissaka gave his side a glimmer of hope with a well-taken finish.
And things got even better moments later when fellow full-back Emerson Palmieri banged in a beautiful free-kick.
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The celebrations from those still in their seats were sure to have tempted fans back from the concourse.
But their collective joy was short-lived.
As West Ham pushed for a third, they ended up conceding a penalty from a corner.
With Odegaard already netting one from the spot, Bukayo Saka got the chance to open his account.
And England's star winger made no mistakes as he fired home to make it 5-2 to Arsenal.
Hammers boss Julen Lopetegui responded at the break by replacing winger Crycensio Summerville with anchorman Edson Alvarez.
But neither side was able to find the net again, with the result sending Arsenal into second while leaving West Ham in 14th.