Let $(\Omega , \mathcal{A})$ be any measurable space, and let $(\mu_n)_n$ be a sequence of probability measures on this space, such that the limit $\mu(A) = \lim \mu_n(A)$ exists for any $A \in \mathcal{A}$.
Then $\mu$ is a finitely additive measure of total mass $1$ on $(\Omega , \mathcal{A})$. Is it always true that $\mu$ is $\sigma$-additive?