Robb said he was concerned about when his wife and daughter would return from the trip because he didn't want his daughter to miss any school.
"The discussion was very tense," Robb said. "We were both anxious."
Robb said his wife pushed him and that's when he lost it.
He went into the living room and grabbed an exercise bar used to do chin-ups and started hitting his wife with it, he said.
"I just kept flailing it," Robb said, moving his hands.
After he explained to the courtroom what had happened, he apologized to his family, his wife's family, and his daughter.
"I know she loved her mother and her mother loved her, and now she doesn't have a mother," Robb said, choking up.
Tressler deferred sentencing for the former Penn professor who specialized in game theory.
He was remanded without bail and remained stoic as he was led away by a court deputy after the proceedings.
His attorneys said Robb told them he had disposed of the incriminating evidence in a trash bin in Chinatown.
Frank DeSimone, one of his attorneys, said Robb called his daughter over the weekend and told her he was responsible for her mother's death.
After the proceeding, members of Ellen Robb's family said that they were satisfied with the plea deal but that yesterday's outcome was only a small step toward healing.
"I think it's clear that Rafi acknowledged his actions," said Ellen's brother, Gary Gregory. "He did so in a forthright manner and we're pleased to see that finally occurring."
"Clearly, she was a . . . ," Gregory's voice trailed off as he became emotional, "a most amazing individual, often described as an angel on earth."
Gregory wouldn't comment on whether his sister had been physically abused in the past, but said her husband's verbal abuse had damaged her.
"Certainly there was clearly long-standing verbal abuse, which eroded my sister's confidence, her joy, and her passion and ability to contribute as she always had earlier in her life," Gregory said.
Gary and his brother Art said that the only thing that kept Ellen and her husband together was their now 13-year-old daughter, Olivia.
Late yesterday afternoon under the drizzling sky, the Gregory family met with reporters at the Roberts Elementary School in Wayne, which Olivia attended.
The brothers spoke about their sister and about a Massachusetts-based foundation established in her memory - Every Great Reason Foundation. (www.everygreatreason.org)
Calling yesterday "a tragic day for our family," Gary Gregory said it was also "a day of healing, a day that allows us to move forward."
"The foundation is focused on the recognition that every person has every great reason to carry forward, move forward to a new life," said Gary Gregory, standing at a gazebo that had been dedicated to Ellen Robb in September.
So far the group behind the gazebo dedication, Friends of Ellen, has raised $8,000 and has scheduled a fundraiser for Dec. 20 at the Radnor Hotel.
Ellen Robb, a Brownie leader, had been an "MVP" at Roberts and "one of the most giving souls you'll ever meet," her brother said. "She gave her heart and soul to the school," he added.
Montgomery County District Attorney Bruce Castor said that from the beginning he had believed that Ellen Robb's murder was a heat-of-passion killing.
He said the withdrawal of the original charge of first-degree murder, gave Robb all the consideration to which he was entitled from the prosecution.
Castor said the prosecution would ask for significant prison time for Robb.
Usually, Castor said, the minimum sentence for voluntary manslaughter is 54 to 72 months in jail but a maximum sentence could be anywhere from 10 to 20 years.
Another of Robb's defense attorneys, Jules Epstein, said that by his client's plea he took responsibility for his actions. "The law defines this crime as exactly what happened," he said. "Passion manslaughter, not malice murder, which is bad people doing evil things, but recognizing the frailties of human emotion. That's exactly what this case is."