It looks like I was incorrect.

This is the record for the donation that the news reported. On the document it states the city of the donor as being "Pittsburgh" and there is another person named Thomas Crooks that lives in Pittsburgh. But the zip code is to "Bethel Park" the town the shooter was from. The street address on the document doesn't seem to matches any street address in Pittsburgh but there is one in Bethel Park according to Google maps.

So I think it probably was the shooter that made the donation.