To understand what's going on, look at
As well as /etc/inittab
Basically, the startup/shutdown scripts are in init.d. The startup "runlevel" is in inittab. rc3.d is for runlevel 3. rc5.d is for runlevel 5. S is for startup. K is for kill.
Be careful with the clamav rpms in the standard yum repositories. I've found them to very flakey.