How does Elias frame Lucas?

In Chapter 52, two civil guards are on patrol, discussing the news that Elías is in the area. They find Lucas and question him, noting his scar, and one wonders if Elías has a similar marking. They let Lucas go and find Elías soon after, but do not recognize him, and Elías claims that a man with a scar named Elías beat up his brother, framing Lucas.