The University of Utah Eccles Health Science Library has an online firearms tutorial available here. It’s easy to use and has almost no bells and whistles (but it has photos!) so you should be able to view this on any computer. I’m not sure when the course was last updated (some of the statistics look old), but the mechanics of firearms and the appearance of gunshot wounds haven’t really changed, so age shouldn’t be a significant issue. It was created for pathologists, meaning it has a medical, rather than law enforcement, flavor.