ScreenCapture2D renders static mesh even when its not ticked in 'General Show Flags'

For dynamic snow deformations, I need to render only the decals onto a render texture and use that texture later as a displacement map. The ScreenCapture cam has decals selected in its ‘General Show Flags’ and nothing else.Yet it also renders the static mesh on which the decal is placed. I also noticed that this occurs only when Material on static mesh has emissive color. Am I missing something ??