[Request] Killing a specific command in Linux?

Ok so i have a question about killing a specific shred process in Linux

I need to kill for example a shred process of many , but i don't want to kill them all.

I need this for a udev removal script for my hard drive wiper i have been working on.

I need to kill the following command "shred -v -f -z /dev/sday"

but when i issue the command killall "shred -v -f -z /dev/sday"

i get the following no such file or directory?

i don't understand why something so basic wont work with a simple command?

any help on this one guys, free rep :)

note: i cant kill the process with PID as the numbers change.
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