Is the category of short exact sequences of abelian groups abelian?

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I've been trying to figure out if the category of short exact sequences of abelian groups is abelian. It's clearly additive, and it has all of its kernels, but Im not sure about cokernels. I can't produce a solid counterexample, and don't know if it exists. Is the category abelian? And if not, what witnesses it's failure? I was thinking of the cokernel of a sequence like 0->Z->Z but I'm not sure (sorry for the poor formatting, I'm on my phone)