Finding sources for the Port Arthur massacre can be difficult due to the amount of conspiracy-theory videos, books, and articles available which posit that Martin Bryant was framed for the shootings. One book which tells a fairly concise story of the events of the day is Martin Bryant: The Port Arthur massacre. The only other book specifically about the massacre which is available and doesn’t suggest Bryant was framed as some sort of conspiracy is Born or Bred? Martin Bryant: The making of a mass murderer, although it does seem to be rather difficult to obtain outside of Australia and I was therefore not able to use it as a source.
Finding non-conspiracy documentary or news footage regarding that massacre on YouTube can also be tricky. One suggestion is to look for videos which specifically tour the historical site at Port Arthur. These videos usually only focus on the location itself, but the employees at the site neither mention the shooter’s name nor question his guilt.
Carleen Bryant did an interview with 60 Minutes in Australia here. She firmly believes in her son’s innocence. Others interviewed in this selection, however, do not.
Australian show Witness had a segment on the massacre which begins with part 1 here.
If you are interested in information about the theory that Bryant was framed, a simple Amazon or YouTube search will provide you with plenty of sources.