Depends how it's fixed to the wall, removed door stop and see if you can see any screw head which you can undo, may have to remove the wood filler, if it's nailed then a hacksaw blade behind the frame to cut the nail etc
if not cut through the frame on each side a couple of times about 6" apart. You should be able to remove the portion and then you can get a crowbar in to carfully prise the rest of.
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