Or another alternative would be to reboot the phone, since the killing
of that app might leave your "credentialmanager" in a bad state.
Either way, it sounds like you were getting constant alerts on it,
which means it was using 90% of your CPU for more than a few minutes.
After rebooting, I'd go into the whitelist and remove it. I'm not sure
what that app does, but it shouldn't constantly be using CPU like
that. And it probably won't do it again. But if it does, you'll want
to be alerted again so you can reboot(which is why I'd take it off the
whitelist).
Robert