"She caught my eye. I thought it was strange that a man his age would be with a child or a young girl," she said.
Shanley says it sent a chill down her arms and once inside the store, she asked a clerk to call police.
"As I was waiting on the phone I thought my God could it be her, but I thought they're in Virginia, why would they come here. But when I was talking to the police officer I said it may be the girl from Virginia," she said.
The girl from Virginia turned out to be 12-year-old Brittany Smith who disappeared just a week before and with her was 32-year-old Jeffrey Easley.
Virginia police say the girl's mother, Tina Smith, was killed sometime on Dec. 3. They say Easley, her live-in boyfriend, is a potential suspect.
The following day, both Easley and Smith were caught on a surveillance tape getting camping equipment at a Walmart in Virginia. From there, the trail went cold and traveled 2,300 miles until Shanley spotted them at the Safeway.
Shanley recognized her after watching a show about the missing girl on CNN. She says it was her big brown eyes that caught her attention.
"She stared at me the whole time as I walked toward her, pass her, to pick up a cart to pulling out the cart. We didn't unlock our eyes," she said.
Easley remains under psychiatric observation and his extradition hearing is scheduled for Tuesday morning. Smith left San Francisco on Monday and was reunited with her family in Virginia.
There is no better feeling than saving a child. So I'm glad I could help her," Shanley said.
Shanley told ABC7 News she never shops at the Ocean Beach Safeway, and that she only made a quick stop to get some dog food. As for the suspect, he said he was clean and shaven as opposed to a picture that showed him a goatee.
ABC7 News learned that the pair came to San Francisco because Easley Googled 'best place to be homeless' and San Francisco came as No. 1.