I did consider this. But if you check your browser's developer tools, the border color is different from the color in the role description. The border is #250000, the word "serial killer" in the OP is dark red, which resolves to #8B0000. And, if Jupiter really was the serial killer, then how did an underdweller die last night?
Of course, it is possible that eros just used a darker shade of red for the border, and it's possible that the SK gets to kill on the same night he himself is killed. I'm just saying that it's not a 100% certain thing.
But, for the sake of looking deeper, I noticed there's a few things that happened last night that haven't been touched on.
Also, maccrash is the granny.