A volunteer with Little By Little, a Chicago-based non-profit group that provides health services to those in need, O'Brien and a group of 24 volunteers had just left the village of Gramothe, where her group had just finished a free clinic.
The village was flattened. O'Brien and the volunteers were unharmed. After a few terrifying hours, during which she witnessed "dismemberments, people dying, all kinds of atrocities," she was able to reach her husband, Terry, by satellite phone.
They spoke for only two minutes, and since then he's been unable to reach her on the phone.
While thankful Stacy was safe, Terry immediately grew concerned about the dangers facing his wife now that all semblance of government control in Haiti was destroyed.
"Stacy has two problems now," said Terry. "One, she's in the mountains and there are no roads that are passable. Two, Port-au-Prince is a cowboy town now."
Electricity and phone service are completely out, and fresh water supplies are dwindling, according to reports. The United Nations secretary general, Ban Ki-moon, said Haiti was facing a "major humanitarian emergency."
The two largest symbols of authority in the country, Haiti's presidential palace and the United Nations headquarters, lie in ruins.
Terry said he's been looking into every available option, including private jets and helicopters. With Haiti's airport inoperable, nearby Dominican Republic seems like the best option, he said.
"We're trying to find any way in," Terry said, mentioning he'd considered hiring helicopters to fly in from nearby islands.
But right now, he's just worried. He hasn't been able to reach Stacy since 7 a.m.
"We're doing everything we can," he said. "Everything we can."