Once he gets past feeling stunned, Thomas runs over to the boy and calls for help. The Runner, whose name is Minho and looks like this, is conscious but utterly exhausted.
He asks Alby, who has come to help, to get him some water. Then Thomas and the Runner have the usual interaction: Thomas asks questions, Minho yells at him for asking questions. For these two, though, this exchange acts as an ice breaker. Geez, get a room you two.
As they're talking Minho reveals that he's seen something special during his run today, and that's why he's so exhausted. When Alby comes back, Minho hits them with his information bomb: today he found a dead Griever.