This was a Dublin derby that dripped with drama both on and off the pitch at Dalymount Park last night.
From the early stages, with the atmosphere raw and tense, it was apparent that incidents were inevitable -- but few could have predicted the staggering final result of this clash that Celtic boss Neil Lennon watched from the stands.
For Rovers, this was a truly dismal defeat to rank with those suffered against St Pat's and Sligo Rovers. It was a chronic loss for the faltering champions, packed with brutal defensive lapses and weak goalkeeping as Bohemians posted an encouraging success.
The flash of violence between the rival supporters that occurred briefly following the first of Peter McMahon's brace captured how edgy the occasion was at the outset.
By the end, though, it was simply a party for the Gypsies as a late double from substitute Karl Moore sealed the deal.
Five all-Dublin tussles in just over a fortnight ensures that Rovers' character and commitment are currently receiving a stern examination and this was a worrying night for them.
Bohemians, undergoing a dreaded 'transitional phase', were keen to disturb Rovers' title assault so there was no shortage of intrigue.
All honest aggression initially, the Gypsies were quickly out of the blocks, snapping into the challenges and denying Rovers any space in the centre of the park, where Aaron Callaghan opted for a five-man unit. In the middle, Davy Mulcahy anchored, while Keith Ward and Ryan McEvoy buzzed about craving involvement, and Rovers were bothered.
Eager to press Rovers as high up the park as possible, Bohs were bright and busy and their enthusiasm was rewarded in the 11th minute. Graham Gartland was dispossessed by Dwayne Wilson, who led the line in splendid fashion and suddenly Rovers were distressed.
Wilson scampered down the right and his cross spilled kindly for Peter McMahon at the back stick. McMahon remained cool, confidently striking Bohemians into a surprise lead and then it was time for a small minority of supporters to clash.
The 800-strong Rovers contingent were in the Old Schoolhouse End and a half-dozen or so of them climbed the fence to enter the playing area. There they were quickly joined by a similar number of Bohemians' spectators before security personnel and gardai reacted.
Within a matter of minutes, two riot police vans whizzed into the ground and matters calmed slightly.
Between the white chalk lines, it took Rovers a long while to provide any real glimpses of their ability. Ronan Finn was prominent, while out wide Gary McCabe and Billy Dennehy did carry a brief threat.
Still Rovers' best opening period chances came via Dennehy free-kicks, one which thundered off the woodwork on 39 and another which crept inches wide on the stroke of half-time.
When the interval rolled around, though, it was the Gypsies who held a one goal advantage and Rovers were completely aware that a response had to be summoned.
But it was Callaghan's gutsy Gypsies who inflicted more damage seven minutes after the restart as another Rovers goalkeeping error proved costly.
Oscar Jansson's attempted clearance lacked conviction and Keith Buckley pounced, dashing into the area. Buckley's cross should have been gathered by Jansson, but it wasn't, and McMahon doubled Bohemians' lead.
Unsurprisingly the celebrations were wild, but the locals had further cause to shout in the 57th minute when Rovers substitute Stephen O'Donnell was red carded. Referee Rob Rogers reckoned O'Donnell was the last man when tripping Ward, who had made a lung busting run.
Then, five minutes from time, Bohemains hit a third when substitutes Dinny Corcoran and Karl Moore combined with the latter making the Rovers net ripple with a sweet strike from an acute angle.
Moore then decorated the victory on 87 minutes when Jansson failed to deal with a routine shot to pile the pressure on Rovers boss Stephen Kenny. With Sligo Rovers winning at Oriel Park the Hoops know that improvement is required fast.
Bohemians -- McNulty; Heary (Barker, 70), McMillan, Feely, Byrne; Buckley (Corcoran, 80), Mulcahy, Ward, McEvoy, McMahon (Moore, 66); Wilson.
Shamrock Rovers -- Jansson; Gilbert (O'Donnell, 46), Oman, Gartland, Powell; McCabe, McCormack (Greene, 79), Finn, Dennehy; O'Neill (Turner, 59), Twigg.
REF -- R Rogers (Dublin).