Bills in the US can originate from either the house or the Senate. If it passes one then it goes to the other. If it passes both then it goes to the President to be signed into law.
E: technically there is an exception that bills for raising revenue have to originate in the house but that the Senate can propose or concur with amendments. But for all intents and purposes the vast majority of bills can originate in either body.
While the comment that you are replying to does lack nuance, the intent is clear. There is obviously a difference between murder and self defense.