Keane spoke only briefly to reporters and became angry when questions focused on the last-minute winner and not a penalty decision given against his side. Iain Hume had missed the second-half spot-kick.
"You've watch the game and nobody's asked me about the bloody penalty," Keane said as he got up to leave. "That about sums you up."
The Irishman then challenged reporters on his way out of the room.
"Was it a penalty? Does anyone in this room think it was a penalty?"
Keane began the press conference in more conciliatory fashion, and insisted there were positives to be taken from the game despite the result, which extends the worst start to a season in club history.
"It's another disappointing result but we deserved more than we got," he said.
"It wasn't a pretty game but we had just about the better of the chances barring the penalty. To concede in injury-time again after five and a bit minutes is hard to take.
"But we knew coming here today would be difficult with the conditions and Barnsley being on a good run of results."
The Tykes led after only eight minutes through Hume's strike and might have added more before Liam Rosenior pounced on a goalkeeping error to head in an equaliser on the stroke of half-time.
"We had a poor start with the goal but we responded well and had some good opportunities," Keane said.
"That's the way it's going for us at the moment. Instead of winning the game in the last couple of minutes you go from the disappointment of that to having a double-whammy by actually conceding."
While the pressure mounts on Keane, the victory continues Mark Robins decent start as Barnsley boss.
"It's back-to-back wins for the first time since I think Boxing Day last year so from that point of view its excellent," Robins said.
"It's a decent return, we've had a decent start. We've been in three weeks now and we're seeing things starting to move. The supporters are behind us, that's really important, and the players are behind us.
"They're putting in the performances now. Sometimes you have to grind it out but if you can do that around teams around you that's an indicator or how you'll perform at the end of the season."
Although they needed Macken to win it with virtually the last kick of the game, Robins believes his side deserved the win.
He said: "I think so, having missed a penalty, hit a crossbar, missed a free shot when it goes in if Ryan Shotton makes good contact.
"They've had one or two chances too where the goalkeeper has made a good save, but the weather didn't help the game.
"It's a great time to a score a goal, there's no chance of a reply," he added.
"The conditions were shocking, atrocious, and they didn't make for a good game of football and I don't think we got one."