Middlesbrough's faltering promotion push suffered another major blow as Adam Randell's 96th-minute header earned Bristol City a 1-1 draw at the Riverside.
Boro thought they were heading for a much-needed victory when substitute Leo Castledine opened the scoring with a 65th-minute strike.
However, after Castledine's fellow replacement, David Strelec, wasted an excellent chance to double his side's lead, Randell headed home Tomi Horvat's corner deep in stoppage time to level the scores.
The draw means Boro have now failed to win any of their last four home games, a run that has seriously damaged their hopes of finishing in the top two.
Randell's header ensured Bristol City avoided what would have been a fifth successive defeat in all competitions.
Boro's dominance of possession was established from the outset, but the hosts were unable to make the most of a couple of early chances that came their way.
Tommy Conway, playing against his former employers, headed over after Hackney swung over an inviting cross, before Callum Brittain's shot was blocked after Aidan Morris pulled the ball back to the full-back.
Adopting a five-man backline, Gerhard Struber's Bristol City side were defensively disciplined, frustrating their opponents to the extent that Middlesbrough's first effort on target did not come until first-half stoppage time - a Riley McGree effort drilled straight at goalkeeper Radek Vitek - despite the home side enjoying 70 per cent of possession before the break.
Bristol City were unable to threaten at all in the first half, but the visitors showed signs of attacking life at the start of the second with Emil Riis cutting infield from the left touchline and driving towards the edge of the area before dragging a low shot wide.
That was the cue for Boro to raise their attacking intensity levels, and the best chance of the game went begging in the 55th minute. Vitek could only parry Aidan Morris' shot into the path of Browne, but from four yards out, the Sunderland loanee fired a tame follow-up effort at the goalkeeper's legs.
Browne wasted another good opening on the hour mark, heading Targett's cross straight at Vitek, but Boro finally opened the scoring in the 65th minute.
Castledine had only been on the pitch for six minutes when he received Hackney's low cross from the right, but the substitute fired home an emphatic first-time finish that clipped the underside of the crossbar before going in.
Boro should have doubled their advantage with nine minutes left, but despite being left with a clear run on goal, Strelec could only roll in a tame shot that Vitek saved with his foot.
It proved a crucial moment, as Bristol City levelled in stoppage time when Randell powered ahead of Adilson Malanda to head home from the edge of the six-yard box.
The managers
Middlesbrough's Kim Hellberg:
"I'm happy about the performance, I think it was an unbelievable performance again. Unbelievable from the players - how we play, how we act, how we create chances.
"It was a top performance, but of course it's tough if you don't kill the game off, there can be an opportunity for a team that maybe have their first chance to score in 95 minutes. That was the disappointment, but again, if you look at the performance, you are looking at a team that have played very good football.
"Of course, it hurts to concede when we did, but in my role, you have to look at the performance and the things we are doing well. I think that the way we play is the most important thing to talk about.
"I know the result, at 1-1, is a disappointment now. It's a team we haven't beaten in a long time - we struggle a lot with this team - but I think the way we play, creating chances, being brave, is very impressive. I think it is stronger for me to tell you that when we have not won. I think we are a hell of a good football team, and I am so impressed by it."
Bristol City's Gerhard Struber:
"It's a special point. Being resilient was how the boys were committed to the match plan. We had a deeper block and were waiting for the transition moments, and that was exactly what we talked about before the game.
"Especially in the first half, we did a great job with our organisation and didn't give them the space they like. We had better transitions in the second half and in the end, we scored a goal.
"We believed something could happen. It was really late, but I would say it was well deserved for the resilience, discipline and the big effort we left on the field.
"It was big team work from us, and we have stopped the bad run. It feels like a bit of a release."
