He used Pathos in the last two paragraphs. When he states "The reason that I have such an intense interest in this topic is that my son was killed by a gun (not my own) that belonged to a person who only wanted to protect his household, but it fell into the hands of a child by mistake." Besides using Ethos, he is using Pathos to appeal to the congressman emotionally by making him feel the grief of having his son killed by a misfire. In the last paragraph, he states "I believe in our rights as citizens of the United States, especially the right to LIFE, liberty and the pursuit of happiness." He wants to appeal through vivid language, through beliefs and rights.
He used Logos in all the other paragraphs. In the sentences "Did you know that, according to the F.B.I., approximately 60 percent of all murder victims in the United States in 1994 (about 16,000 people) were killed with firearms? According to estimates, firearm attacks injured another 70,000 victims, some of whom were left permanently disabled." and "Only 2 of the 743 gunshot deaths occurring in the home involved an intruder killed during an attempted entry." He is showing statistics and hopes that the significance of the numbers can make the congressman realize something.