Since it sparked a public scandal, you can think to how people feel about scandals. After getting more info about the Petrov Affair, people were probably felt angry, betrayed, and shocked. (Probably mostly shocked, and maybe some even began to form a prejudice against Russians?)
To help you could see if you could find any quotes about it, on how people felt from maybe news articles or something. You can also go on the history channel's website.
Hope this helped! Good luck!!