Family Guy episode 17

Season 4

Lois discovers she has a brother named Patrick and therefore takes the family cross-country to meet him. However, it turns out that he's in a mental institution, but Lois thinks he's sane, so she checks him out to live with the Griffins. Meanwhile, Peter starts a Society for the Acceptance of Fat Men. However, the fat men of Quahog are strangled one-by-one.so the Fat Society live in terror. Who is the strangler?