Does the sprockets on his wheel spin at all? It's hard to make out from the pic, but it looks like he might have some funky two speed fixie arrangement on there.
If it's a "real" fixie I don't think you'll be able to fit a regular freewheel on there, but if it's something cobbled together out of a originally freewheel hub it should be OK. Lockring tool or hammer + drift punch. Regular hub it should unscrew counterclockwise.

What you are referring to as "the bolt" is probably the axle. Axle and cones needs to match up for the bearings to work. Not so good odds of sucessful random matches.

I first thought that you might have the dreaded helicomatic hub, but probably not.
There are at least 3 different splined freewheel pullers. Either swing by a bike store and have them remove that one for you for a few bucks, or get us a solid measurement of the diameter of the splined cavity. Vernier caliper is recommended.