Wouldn't sweat it. That's not a threat of a lawsuit. Statute of limitations would apply. Sounds more like a threat of extortion.
Not so fast either. If this gets spun into some kind of sexual assault, he could even STILL be prosecuted criminally. In many states the statute of limitations stops if you “flee” the state.
Say it had a stature of limitations of 6 years,, and two years after the incident, he left the state. That will be him “fleeing”. This is deadly serious and he needs to never speak about it, ever,,, to anyone except on advice of counsel.
I've read that some states have changed their statute of limitations laws in cases like this.