The writer has used ethos by elaborating on the perils of possessing guns in his country to persuade the congressman to support the gun control legistration. He also seemed very professional in his letter by taking his stance as someone who was strongly against the possession of firearms, thus the letter would appeal to the congressman.
He has also used pathos, or emotional appeal, by complimenting the congressman himself, before stating that he has a personal experience of losing his own son due to guns and firearms. The writer also had some rhetorical questions in the letter to set the reader thinking, and he also wrote how the buying of guns in America could affect the nation itself, so as to convince the congressman to support the gun control legistration.
Logos, however, is the most commonly used form of persuasion in the letter. The writer stated a lot of statistics in the letter to convince the reader to change his mind. He wrote the percentage of murder cases caused by a gun, number of disabilities caused by a gun, total cost of injuries cost by shootings, and that the possession of guns increase the risk of killing a household member or friend, rather than an intruder.