You may think at first there is one vocalist. Nope, there are two! The first screamer you hear at 0:16 with the more lower, raunchy screams is Gus. And the second screamer at 0:20 with the more louder and higher mids is Michael Barr. I like the idea of having two vocalists because it adds more effect to their style and music.
Also, Michael Barr does the clean singing in this song. This band never really used clean vocals in their previous except two with a guest vocalist. I never knew it was Michael who sang it, but the band did confirmed it. I hear it a couple more times, and I kinda hear it better and know it’s Michael voice (I’ve seen some interviews with him).