A note on the universal supersingular quotients of $U(2,1)$

Let $G$ be the unramified unitary group $U(2,1)(E\mathrm{/}F)$ defined over a non-archimedean local field $F$ of residue characteristic $p\mathrm{\ne }2$. In this note, we prove the universal supersingular quotients of $G$ are not irreducible in general.