It helps create uneasiness.
Characterization is the way an author presents a character. In this excerpt the characters are described as "gangsters". It says that they are "eyeing" the migrants. The narrator also explains that the gangsters are wearing "white plastic rosaries...so the migrants will be less suspicious". These details create a feeling of uneasiness because the men are not described in a positive way and their behavior raises suspicion. There is also no evidence of calmness, hope, or trust in any of the descriptions of the gangsters even though the gangsters want to seem trustworthy and good.