It has been reported, and not contradicted, that it was a "Mauser" bolt action. That would tend to mean a Mauser Gewehr 98, the standard issue German Nazi rifle of WWII, one of these:
Like it probably looks, that sonofabitch is nearly four feet long and chambered for an obsolete and nigh-impossible to find cartridge. So it probably wasn't one of those.
BUT, after the war, the "actions," the bolt, receiver and magazine, were often rebarrelled (you almost literally unscrew the barrel and fit another one) into standard cartridges like .30-06 etc. and restocked into more conventional hunting rifles.
Those are not terribly uncommon and, if well done, prized by collectors and shooters alike. The Mauser 98 "action" is the design foundation of the modern bolt action rifle. In one sense, you could argue that just about any bolt-action rifle he used was a "Mauser action," but that's not the way that would be reported by LE or journalists today.
But, are pretty uncommon in the hands of 20-somethings unless inherited or possibly purchased at a gun show. It's not something you can pick up at Academy, or Dick's or Scheels or whatever the fuck they have in Utah.
So, yeah, it's pretty highly likely "Dad's gun," or one that Dad had a significant hand in acquiring for ol Tyler.