Rules Question - stealth

By Strabaisen, in Deathwatch Rules Questions

Heya Guys'n'Gals of the Imperium.

I'm new here at the forums and wanted to ask some questions regarding "Deathwatch" rules, regarding the use of stealth.

I'm a GM and have a campagin, wherein the team, is a Raven Guard (RG), whom I don't agree on the use of the rule. I know I can "GM Overules" but I don't want to do it that way, just because I can. I want to be sure..

So to make the Scenario.

The RG player stealths(8-10 successes - Awesome) around with a astartes stalker /w. stalker rounds - which is understandable. He doesn't want to be found . He sees a prime target and decides to take it out. He aims (half action) and shoots while making a free action called shot (-20 penalty - to make a headshot!). now I know the stalker does say he cannot be heard. But doesnt the attack make him visible?

I understand it like "a player needs the time (half action) to make the stealth attampt to hide again". - round 1, take aim (+20). round 2, called shot and hide. So the RG needs to use 2 rounds to make use he can never be seen. Or can he kille anything in stealth, and never be seen?

Thanks for any future answears..

-Strabaisen