Jamie Cureton shoved Southend a step closer to relegation from the Coca-Cola Championship with a superb hat-trick as classy Colchester won the Essex derby at Roots Hall.
Cureton latched onto a defensive howler from Efe Sodje to fire the Us ahead after just 37 seconds, doubled their lead with a stunning 20-yard effort and finished off the Shrimpers with a classic poacher's third to make it 21 goals in a prolific season.
Southend kicked off knowing victory would offer at least a temporary respite from the relegation zone, but defeat leaves them with an uphill battle to avoid the drop back to League One.
All too often this season they have been architects of their own downfall, and while Steve Tilson's men enjoyed plenty of possession, Sodje's early Easter present left them chasing the game from the off.
The Shrimpers were promoted ahead of their county rivals last season, but it is Colchester who have exceeded all expectations and remain in with a slim chance of the play-offs following a third straight win.
They also secured local bragging rights with a 3-0 win at Layer Road in November, in which Southend skipper Kevin Maher accused opposite number Karl Duguid of getting him sent off - one of three red cards in a stormy encounter.
Duguid was predictably barracked as he took a throw-in in the opening moments, but Southend's defence were all at sea as the ball was moved across the pitch.
Peter Clarke skied his clearance on the edge of the area and Sodje attempted to guide the ball back to Darryl Flahavan, but only succeeded in teeing up Cureton, who hit a first-time volley past the stranded home goalkeeper.
Shell-shocked Southend attempted to hit back and Maher and Richie Foran sent long-range efforts over the crossbar before Freddy Eastwood got his first sight of goal.
The striker, who is being courted by Wales, found room on the edge of the area and unleashed a trademark curler which forced a fine diving save from young Us keeper Dean Gerken.
Gerken nearly gifted Southend a leveller as the interval approached when his clearance hit Eastwood, but the forward could only deflect the ball wide.
Tilson threw on Jamal Campbell-Ryce for Foran at the break, but it was the Us who almost started the second half as they had the first.
A sweeping move involving Chris Iwelumo, Richard Garcia and Cureton culminated in a shooting opportunity for Kevin Watson which Sodje bravely blocked.
Southend settled once more, though, and Alan McCormack shot low at Gerken before Eastwood should have done better with an angled turn and volley which he fired across goal.
Duguid, revelling in the role of public enemy number one, was caught late by Eastwood as he cleared but the ball still reached Cureton whose lob sailed over.
Gerken preserved Colchester's lead with a smart save from Clarke's header, and Cureton immediately provided the sucker-punch, collecting Iwelumo's chest-down, sauntering forward and unleashing an unstoppable 20-yard shot past Flahavan.
Eastwood fired another effort from distance before squandering his best chance, heading over from close range.
And Southend were made to pay when Chris Barker overlapped down the left and played in Cureton to steer the ball past Flahavan for his sixth goal in three games to cap another fine win for Colchester and leave the Shrimpers in deep trouble.
Teams:
Southend Flahavan, Hunt, Sodje, Clarke, Hammell (Harrold 77),Gower, McCormack, Maher, Foran (Campbell-Ryce 46), Eastwood,Bradbury.
Subs Not Used: Collis, Barrett, Francis.
Booked: Maher, Harrold.
Colchester Gerken, Duguid, Baldwin, Brown, Barker,Garcia (White 88), Watson, Izzet, Jackson,Cureton (Ephraim 83), Iwelumo (Guy 72).
Subs Not Used: Davison, Elokobi.
Goals: Cureton 1, 63, 79.
Att: 10,552
Ref: K Friend (Leicestershire).