Samsung Galaxy S4 Mini wont power on properly

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My wife's Samsung Galaxy S4 mini just powered itself off and now the only thing i can get it to do is to get it to the Warning!! screen with the option of selecting Volume Up.... and sticks at the downloading screen.... or Volume Down Cancel (Restart phone) either way nothing happens... i have take the battery out and re-inserted it on numerous occasions .... removed simcard and sd card.... any idea on how i can get this phone back up and working again.... or is it at the stage when she needs to get it replaced? any assistance would be much appreciated

Thanks

Peter