I could not find a way to remove the camera shutter sound on the OnePlus One phone, but there is a workaround (if you have root on your device): Renaming the sound file!
Instructions:
Open a terminal
Enter “su” to become root
Remount the /system partition read-write in order to make changes (“mount -o remount,rw /system”)
Rename the camera sound (“mv /system/media/audio/ui/camera_click.ogg /system/media/audio/ui/camera_click.ogg.bak”)
Remount the /system partition back to read-only (“mount -o remount,ro /system”)
Done.
Copy n paste way (if you use adb):
su
mount -o remount,rw /system
mv /system/media/audio/ui/camera_click.ogg /system/media/audio/ui/camera_click.ogg.bak
mount -o remount,ro /system