Still in disbelief, Mike Walsh is concerned his son was "out of his mind" when he committed these crimes.
"I know that when Ben realizes what he did last night he will be devastated," Mike Walsh said.
Mike Walsh said he is mentally and physically exhausted after surviving stab wounds allegedly inflicted on him by his own son.
Police say Ben Walsh showed up to the restaurant where his parents were attending a family party and stabbed his mother in the abdomen with a large kitchen knife.
People at the restaurant, including owner Jerry Gaita, had to hold Ben down until police arrived.
"It just seems like he came here on one mission," Mike Walsh said.
Mike Walsh said he thought they were the only ones attacked until they learned Ben had stabbed his girlfriend to death before showing up at the restaurant.
"My son, my other son, called the Needham Police and asked them to check on Ben's girlfriend, and we didn't hear anything else," Mike Walsh said. "I think I was in the emergency room when I saw on television there was a fatal stabbing in Needham and that's when I feared it was her."
Police found she was stabbed to death.
Mike Walsh said although his son had a history of mental health and substance abuse issues, he never imagined he would harm his mother, much less his girlfriend.
"She's, you know, a person he relies a lot on for support. I know she's not a person he would ever want to hurt," Walsh said.
Mike Walsh said he and his wife are mourning the loss of a dear young woman.
"You know, we didn't ask for this, we're doing the best we can to help Ben through all his problems, we were very engaged with medical professionals, we have been," Mike Walsh said. "So we just need space."
Walsh has not yet been charged with any crimes, but police say they expect to file charges soon as the investigation continues.