"We all looked toward the front door. We saw the security guard backing up, reaching for his weapon. And we ran," she said.
MORE: At least 10 dead in mass shooting at Buffalo, New York, supermarket in alleged hate crime
Stanfield's 20-year-old daughter Yahnia Brown-McReynolds was also working at the store when the attack took place.
"I heard all the gunshots. I heard all the bodies fall. I heard everything. It was terrifying," Brown-McReynolds told "GMA" on Monday.
In the commotion, Stanfield said she realized she was separated from her daughter.
"I didn't know where she was. And I just thought, if she's gone, I gotta get out of here. She's got babies -- she has a newborn, and she has a 3-year-old, so I still had to get out. If I went back for her and she was gone, I would be gone, too. And then they'll have nobody," Stanfield said, overcome with emotion. "So I still ran and ran out the back."
MORE: Retired cop who confronted gunman in Buffalo shooting hailed as hero
Stanfield later learned her daughter was crouched down by a register during the gunfire and witnessed two people get shot.
Stanfield said her daughter "covered her face" when the gunman walked by so he "wouldn't hear her breathing."
"By the grace of God we got out," she said.
Brown-McReynolds said her mother would not let her go once they were safely reunited.
"I'm like, 'Mom, I need to breathe.' She did not care. As long as I was breathing next to her," she said.
SEE ALSO: Buffalo community unites in grief and hope following mass shooting
Stanfield and her daughter were among those who escaped alive on Saturday when a gunman killed 10 people -- all of whom were Black -- at a Buffalo supermarket. Authorities are calling the massacre a "racially-motivated hate crime." The 18-year-old suspected gunman is in custody.
Annette Parker and her 9-year-old daughter were walking out of a Family Dollar store, just a few feet away from the grocery store, when they heard gunshots.
Parker picked up her daughter and started running, she told ABC News.
"My mother lives down the street ... so I ran towards her house," she said.
WATCH: US saw 312 gun violence incidents this weekend
Parker said her daughter is terrified, and they're staying with family.
But Parker, with tears in her eyes, said hate won't stop her from going back.
"That's not gonna stop me or my daughter. This is my community," she said.
ABC News' Stephanie Ramos, Katie O'Brien, Briana Stewart and Matt Foster contributed to this report.