check to see if the keyway is still lined up or it it jammed from rotation if not,
you can use a puller from harbor freight you need to thread in a bolt at the end of the shaft so you do not damage it first. then use an impact to trun the puller, wrap a rag around the assembly when doing this also, the key may come flying out at you, and it may make a "pop" noise also, it scared the hell out of me the first time, like a gun shot! LOL
That is the oil pump chain and since your in there, you should put on a new one, this in turn drives the water pump off then off the end of the oil drive shaft.
hope this helps