"I don't know there's a day we don't think about Erin," said Celeste Peterson of Centreville, Va. 

Erin Petersen, a freshman at Virginia Tech in 2007 was one of the 32 people killed by student Seung-Hui Cho. She had been a star basketball player at Westfield High School, which was also Cho's high school. 

Erin was Celeste and Grafton Peterson's only child.

RELATED: Virginia Tech remembers victims

"It's like a bomb going off in our life and Graf and I were standing really close to where the bomb sent off," said Celeste, describing the waves of grief, "shrapnel" that in inflicted family and friends of Erin. 

One of her very close friends was Shelby Lennox who had played travel soccer with Erin for eight years throughout their childhood.  

Lennox's mother Cheryl and Celeste also become great friends. When Erin died, Cheryl was a constant source of comfort always by Celeste's side. 

"As people started fading away, she was still here. We would sit and not say anything for hours. I would look at her and she'd look at me and I would start crying and she would cry...It meant everything to me," said Celeste. 

The mothers' deep friendship is evident in they way they finish each other sentences,  their inside jokes and their shared grief. 

When Cheryl's daughter Shelby was planning her wedding, Cheryl said, "she knew she wanted Grafton and Celeste to be part of the wedding."

They asked Celeste to officiate and Shelby asked Grafton, her best friend's father, to help walk her down the aisle. 

"I wanted her parents to be able to be a part of a wedding because they weren't going to have that opportunity with Erin," said Cheryl.   

RELATED: Virginia Tech honors Orlando community after shooting

Celeste spent weeks writing the vows.

"When it was finished and I read the vows to you, we sat here and boo-hooing," said Celeste.  

She says she and Grafton were very moved to be part of Shelby's wedding.

"He didn't want to cry, so he gets quiet. So he got real quiet. But he kept commenting, 'You wrote those vows? That was really good.'" 

The families were thankful Grafton was able to be there as his diabetes was taking a toll on his body. He was very sick. Six months later, Grafton Peterson died and was buried next to Erin. 

"It was the same cast of characters, here we go again," said Celeste, referring to her close networks of friends who once again sat by her side.