Port Arthur is associated with more than one historical massacre, so the answer depends on which event you mean. Most people asking this question are referring to the 1996 mass shooting in Tasmania, Australia.
Port Arthur, Tasmania (1996)
In the Port Arthur massacre in Tasmania on 28–29 April 1996, 35 people were killed.
In addition to those killed, around 18–23 people were wounded in the attack.
Port Arthur, China (1894)
There was also a Port Arthur massacre in 1894 in what is now Lüshunkou, China, during the First Sino‑Japanese War.
Estimates of the number of people killed in that event vary widely, from a few thousand to tens of thousands, and historians still debate the true toll.
If you say which Port Arthur you are interested in, more specific detail can be provided.
