As he was watering the lawn of his West Texas home, a hole opened in his yard.
The sprinkler ended up in a tunnel that had collapsed.
Now, Texas Tech historians are trying to figure out what's beneath Smithwick's property.
Texas Tech curator Scott White says the tunnel is an "interesting mystery."
A local television station reports that experts believe the tunnel constructed after a rail line was extended in the early 1900s.
It's likely the city will order the tunnel filled in for safety reasons.