"But I was worried and a little freaked out. I couldn't really focus at work," she said.
Yi was trying to reach her mom by phone, but didn't have a number for her at work and her mom's cell phone was in her car. She finally got her around noon and that's when she realized how close her mom was to danger.
"Once I found she was there and they were on lockdown and she was so close to harm's way, I broke down at work. I said I had to go," Yi said. "I wanted to go home and be ready to go get her."
Yi said her mom didn't see anyone get shot nor did she see anyone who was injured, but a lot of people in her office knew the people who were killed or hurt.
"She was listening to stories from them. And one woman in her office, when they walked out of the building, was covered in blood. In a mad scramble to get out, she was covered in blood, but doesn't know how," Yi said. "There are lots of horrific stories, I'm glad she didn't have to experience them first-hand. To be in the midst of it must be really crazy."
Yi sat at home "waiting, waiting, waiting" to hear from her mother again. She waited about four hours, until about 4 p.m. when Richardson called and asked her daughter to come get her.
"She was just her regular, cool self. 'I'm at Nationals Park, can you come get me?'" Yi said of her mom, who called from a borrowed phone.
"I got up, shot out the door and got there as fast as I could," Yi said, adding that the stadium is usually about 20 minutes from her house.
Once she got there it was a different story. Yi said she must have circled the parking lot eight times.
"I kept seeing the same traffic people, who told me to go to the next light, go to the next light. At one point I started crying and one guy felt sorry for me and told me to go down one street. That didn't work either," she said.
Eventually, someone told her to park and walk, which she did. When Yi got to the garage, her mother was sitting on the curb waiting. She was one of the last people to be picked up.
"Finally I got to her. Of course, I cried more than she did," Yi said. "I just felt relief. All day I couldn't stay calm until I knew she was safe and sound. I was relieved to be able to take her home."
Yi joked that her mom looked a little pitiful sitting on the curb by herself, and a little like a refugee with her small bottle of water. And as they walked back to the car, Yi couldn't help but think how hungry her mom must be, since she hadn't been able to really eat.
"I was just thinking how traumatic it must have been for her," she said.
As they left the garage, Yi and her mom were swarmed by the media.
"We must have looked pitiful," she said.
Twenty-four hours later, "it almost feels like it didn't happen," Yi said. "I'm back to life as usual. I came into work, at 7:30, do my thing. I know she's safe at home. I'm dealing now with the new-found fame thing more than anything."