R2 whistles

[Andy]

NFHS rules

I am R2, working with an R1 that I have worked with many times before. HS Varsity match.

Rally in progress, ball is sent over the net by team S, kind of a looping path, team R player takes a swipe at it to hit it but just barely ticks the ball, I hear, as well as see the contact. Team R then passes, sets, and attacks the ball. I see this periphially as I am now on the team S side.

I am discreetly signally a four contact violation to my partner, but she does not see me. Team S coach is yelling "FOUR, FOUR". I blow my whistle as I am 100% sure of the violation.

Question.....is it proper for the R2 to whistle on that call?