Redirecting stdout and stderr while duplicating stderr to another file in bash

I'm trying to redirect some bash script outputs. What I whould like to do is :

./some_script.sh 2> error.log >> all_output.log 2>&1

I whould like to put the stderr in a file, and both stderr and stdout on another file.

In addition I want to append at the end of all_output.log (for error.log that doesn't matter).

But I'm not getting the right syntax, I've been trying lot of things and I wasn't able to find out the right thing to do.

Thanks for you help ! :)