In an interview on ABC’s 20/20 Friday night, the parents of murdered mom Shanann Watts spoke of their grief after losing their only daughter and grandchildren.

Sandra and Frank Rzucek, Shanann’s parents, sat for their first interview since their daughter and two granddaughters, 4-year-old Bella and 3-year-old Celeste, were found dead by the hand of Chris Watts in mid-August.

“Those grandchildren … they were my everything, they were my only grandchildren in the whole world,” Sandra said in the interview.

Thought the Rzucek’s had for years loved Chris Watts and believed their daughter was extremely happy with the “perfect life,” they described how things abruptly changed this past summer

Chris began behaving differently “a few weeks, maybe a month” before the murders, Sandra said. “Just cold as ice, and not responding.”

During most of the disconnect, Shanann and the girls were visiting their family in North Carolina.

“[Shanann] just couldn’t understand why he was so cold.”

Chris Watts came to meet them for the final week of the summer trip, but things weren’t right between them. Shanann began confiding in her friends about her husband’s sudden distance.

“He’s changed,” Shanann wrote in a text message to a friend read on 20/20.

“I don’t know who he is.”

In November, Chris Watts pleaded guilty to murdering his wife and daughters, and is now serving five life sentences without the possibility of parole.