Updated

The pro-Obama super PAC is continuing to blast Mitt Romney's work at Bain Capital in a new ad, in which a former worker at a plant that was acquired by the private equity firm and later closed said he was forced to "build his own coffin."

The Priorities USA Action ad features Mike Earnest, who worked at the paper company Ampad in Marion, Indiana. Bain acquired Ampad in 1992; the company filed for bankruptcy in 2000.

"Out of the blue one day, we were told to build a 30-foot stage," Earnest says in the ad. "Just days later, all three shifts were told to assemble in the warehouse."

"A group of people walked out on that stage, and told us that the plant is now closed, and all of you are fired," he continues. "I looked both ways, I looked at the crowd, and we all just lost our jobs. We don't have an income."

"Turns out that when we built that stage, it was like building my own coffin," Earnest concludes. "And it just made me sick."

"If Mitt Romney wins, the middle class loses," the final on-screen text reads.

While some high-profile Democrats have expressed discomfort with attacks on Romney's private equity career, President Barack Obama's re-election campaign and the pro-Obama super PAC have continued to accuse the Republican candidate of building his fortune at the expense of the middle class.

On Friday, Obama accused Romney of being an "outsourcing pioneer" at Bain.

According to Politico, this is the fourth ad in a five-state buy by the super PAC.