Gary Twigg scored twice inside two minutes late on as Shamrock Rovers snatched victory from the jaws of defeat to prevent arch-rivals Bohemians regaining the leadership of the Premier Division table.
The win, their biggest yet under new boss Michael O'Neill, moves Rovers level on points with Derry City - whom they meet at the Brandywell next week - in third place. A third defeat of the season, and second on the spin, see champions Bohs now trail leaders Cork City by three points.
Rovers were unchanged from their 3-0 win in Sligo last week with Padraig Amond, who scored twice in that game, keeping his place ahead of the fit again Dessie Baker.
Bohs made the one change with Anto Murphy making a first league start in six weeks on the right wing as Graham Carey dropped to the bench.
After some innocuous early probing at either end, the game sparked into life on 15 minutes when Bohs took the lead.
A loose clearance from Rovers’ defender Aidan Price gifted the ball to Murphy and he was tripped by the backtracking Rovers skipper Shane Robinson.
Cork referee Alan Kelly didn’t hesitate in pointing to the spot. Up stepped the in-form Byrne to confidently drive home the penalty for his eleventh goal of the season and a milestone 150th league goal of his career.
Rovers were struggling to find any rhythm and Bohs looked comfortable as they controlled midfield.
Barry Murphy’s goal remained the busier throughout the first half with the Rovers keeper having to tip over a Killian Brennan free-kick from long range while Byrne looped a header over the bar from Murphy’s cross on 39 minutes.
Glen Crowe then looked set to double Bohs’ lead on 44 minutes, but volleyed wide when Paul Keegan’s header caught Rovers at the back.
Rovers had to be better on the resumption and they were with Twigg twice coming close with headers inside ten minutes, the second he really should have done better than plant wide from Ollie Cahill’s super cross to the back post.
But Scot Twigg made amends to turn the game on its head inside 90 dramatic seconds late on.
The equaliser came on 88 minutes when Twigg somehow hooked home when Stephen Rice’s shot deflected to him in a crowded area.
Scarcely 90 seconds later Twigg won the game when meeting Price’s free-kick to loop a header over Brian Murphy and into the net for his tenth goal of the season, and a goal that sent Tallaght Stadium into raptures.
Shamrock Rovers: Murphy; Flynn, Maguire, Price, Cahill; Bradley, Rice, Cameron (Baker, 62 mins), Robinson (O‘Connor, 42 mins); Amond (Purcell, 74 mins.), Twigg.
Bohemians: B Murphy; Shelley, McGuinness, Heary, Powell; A Murphy (Rossiter, 79 mins), Keegan, Cronin, Brennan; Crowe (Fenn 45, first half), J. Byrne.
Referee: Alan Kelly (Cork).