Brighton picked up their first ever Premier League away win with a 3-0 victory at West Ham on Friday Night Football, which turned up the heat on boss Slaven Bilic.
A double from Glenn Murray and a fine José Izquierdo effort mean the Hammers have made their worst start to a season since 2010, taking just eight points from nine games.
When Murray stroked home Brighton's third from the spot 15 minutes from time, it triggered a mass walkout from the home supporters - with some aiming their frustration towards the West Ham owners in the directors box.
Brighton defensive duo Lewis Dunk and Shane Duffy were the foundations of a tenacious performance - making it 21 wins from 37 games when they have started together as a pair.
The result moves the Premier League new boys up to 10th in the Premier League.
In Chris Hughton's 100th game as a Premier League manager, the Seagulls sensed nervousness in West Ham's play and struck an unlikely opener.
Pascal Gross maintained his run of being involved in every one of Brighton's goals this season by whipping in a free-kick which was flicked home by Murray with just 10 minutes on the clock.
The response from the hosts was limited - they dominated territory but lacked cutting edge as Duffy and Dunk repelled anything that came into their box.
Brighton, sensationally, doubled their lead in first-half stoppage time.
Joe Hart had to be alert to parry away a fantastic opportunity for Murray but seconds later he was picking the ball out of his net. Izquierdo cut off his left wing before unleashing a curling shot that found the top corner from 25 yards - Hart got a hand to it, but could not keep it out.
At times in the second half, the vocal Brighton travelling faithful serenaded their team with "olés" as their team kept the ball past a static Hammers midfield.
Murray was denied by Hart minutes before he was sent tumbling inside the area by Pablo Zabaleta on 75 minutes. The former Palace man stepped up and fired home.
That goal cued a mass exit in the home end, seemingly leaving huge questions for Bilic and his board to answer.
Man of the match - Glenn Murray
This man loves playing West Ham. His double here made it five goals in seven appearances against the east Londoners. Some have questioned his ability to lead the line at the top level but he's made a career of proving people wrong. This performance showcased everything he's about: providing a platform for others to shine and taking chances when they come his way.
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- This was West Ham's heaviest home league defeat against a newly promoted side since losing 5-1 to West Bromwich Albion in November 1931.
- The Seagulls end the day in the top half of the top flight outside the month of August for the first time since October 1982.
- Since Bilic took charge of West Ham, the Hammers have conceded 18 penalties in the Premier League - four more than any other side.
- Murray has scored two braces in the Premier League - both against West Ham, also scoring twice against the Hammers for Crystal Palace in February 2015.
- West Ham have conceded more headed goals than any other Premier League side this season (5) - they only conceded four headed goals in the entirety of Slaven Bilic's first season in charge in 2015/16.
What's next?
The Hammers face a midweek trip to north London to face Tottenham in the fourth round of the Carabao Cup, live on Sky Sports Football, before tackling another London derby next Saturday against Crystal Palace at Selhurst Park.
Meanwhile, Brighton are back in front Sky Sports cameras next Super Sunday when they host Southampton in the early kick-off.