The couple's New York neighbours tell American tabloid the STAR that the pair have had disagreements over the black Labrador puppy that Moder, 34, gave his wife as a wedding present.
A neighbour says, "They couldn't even agree on where the dog should be."
The neighbour claims to have once watched a disturbing scene develop on the couple's posh Gramercy Park apartment balcony over whether the dog should live in the house or on the balcony.
The eyewitness recalls, "I saw Danny chase the dog on the balcony, swearing at it and yelling.
"The dog had no clue what was going on. It was freaking out."
According to the source, Moder started pelting the dog with snowballs before appearing to kick it -
The neighbour adds, "I heard a yelp. It was loud and heartbreaking."
As the dog yelped, 35-year-old Roberts appeared on the balcony, says the source, who notes, "She was speechless."
When they got back into the apartment, a loud and raging argument between the pair ensued, says the source.