Brand new severe stuttering in a 6 year old

Brand new severe stuttering in a 6 year old Hey all! I need perspective and advice. My 6 y/o has developed a severe stutter over the past couple months. Neither parent has ever had an issue. No family history at all. Kiddo has no developmental delays and has always been advanced in verbal skills. Huge vocabulary and a nonstop talker, but out of nowhere can't get words out. The frustration is all over their face and it's heartbreaking to watch. How concerned should I be? I don't want to over react, but the change is dramatic.