Motherwell put their recent troubles behind them with a five-star display against a stunned Kilmarnock.
Kerr could not conceal his delight after grabbing Motherwell's third
Richie Foran slotted home from inside the six-yard box on 15 minutes after a goalmouth scramble.
The Fir Park side made it 2-0 in 20 minutes when Mark Reynolds headed home. Brian Kerr's 25-yard drive (23) gave Well a handsome cushion at half-time.
Scott McDonald sealed an incredible win for the bottom SPL side with a header (82) and a cool finish (86).
Both sides were intent on getting the ball forward quickly and Killie hit the woodwork in the sixth minute.
A near-post corner from Gary Wales on the left was met by Danny Invincibile, who headed against the bar from six yards.
Jim Paterson sent in a teasing cross at the other end after his corner was cleared, but Steven McGarry was a yard away from connecting.
But Richie Foran gave Well the lead in the 15th minute despite protests from Killie.
Scott McDonald sent in a cross from the left which Frazer Wright sliced wildly towards goal.
Graeme Smith kept it out but Foran forced the ball home as the Killie keeper tried to pick it up.
Reynolds added to Kilmarnock's agony in the first-half
The visitors complained, but Foran looked entitled to make the challenge.
Motherwell went two up in farcical circumstances five minutes later.
Paterson's in-swinging corner was headed on by Mark Reynolds and the ball spun off David Lilley's leg and into his own net.
Well were three ahead in 23 minutes when Paterson played a neat pass to Brian Kerr on the edge of the box and he found the far corner with a beautiful, curling effort.
Killie were looking for a lifeline and twice appealed unsuccessfully for handball in the box after the ball bounced up and onto Paterson's body.
Both were denied and Paterson sent McDonald clear at the other end with a long ball after the second claim.
The Australian was jockeyed wide but opted to shoot despite having McGarry unmarked in the middle and Smith beat away his effort from 15 yards.
Peter Leven saw a 25-yard free-kick hit the Motherwell wall after coming on for Colin Nish and David Fernandez's effort was deflected wide after he re-directed Allan Johnston's misplaced shot.
Johnston headed Leven's cross a yard over as Killie continued to press.
Scott McDonald, who had spurned two chances earlier when sent through on goal, made amends with a quick-fire double on 82 and 86 minutes to complete the rout and compound Kilmarnock's miserable afternoon.
Motherwell: Meldrum, Quinn, Craigan, Paterson, Kerr, Lasley, Reynolds, McGarry, Foran (Fitzpatrick 85), Elliot (Clarkson 83), McDonald (McCormack 88). Subs Not Used: Graeme Smith, Kinniburgh, McBride, Connolly.
Goals: Foran 15, Reynolds 20, Kerr 23, McDonald 82, 86.
Kilmarnock: Smith, Grant Murray (Di Giacomo 75), Frazer Wright, Lilley (Naismith 36), Hay, Fowler, Johnston, Invincibile, Wales, Fernandez, Nish (Leven 59). Subs Not Used: Harpur, Dodds, O'Leary, Adams.
Booked: Johnston, Nish, Fowler.
Ref: C Thomson