If $ p=i+1, r\in \mathbb{Z}[i]$ , $ f(x)=x^n-r$ is reducible in $ \mathbb{Z}[i][x]$ and $ p|r$ then $ 2|r$ .

I know that Norm$ (p) = 2$ and since $ f$ is reducible we get $ f(x) = g_1(x)\cdots g_k(x)$ into linear factors. But from here I don’t know where to go.