Used to work in management in a distribution center. The company had fallen on tough times and there were a lot of rumors going around about layoffs and a lot of people were understandably concerned, and morale was quite low. So one day after this big budget meeting at corporate they ran the numbers and told us that, good news, there would be no layoffs in our department.

So the GM had everyone meet in the break room, probably like ~60 people and acknowledged that while the company was in rough shape, we'd just been assured that there would be no layoffs. Everyone was relieved. Whew, great.

Well just before we're about to close up for the night we get another call from corp; there had been another meeting and they decided that, oops, we have to axe 1/3 of the workforce after all and, oh, effective immediately. So they had to decide which 20 would be the lucky ones. That next morning they had a manager at each entrance and anybody who was on the list was sent to the conference room and told the bad news. Credibility shot. Morale disappeared. Company eventually (mercifully) died.

tl;dr, joyously told everyone at work their jobs were safe and then fired 1/3 of them the very next morning.