Why were Serbian nationalists angry when Franz Ferdinand of Austria Hungary visited Bosnia?

Serbian nationalists were angry because Bosnia and Herzegovina, which had been annexed by Austria-Hungary in 1908, was historically regarded as part of Greater Serbia. Franz Ferdinand was seen as an advocate of a policy known as "Trialism", which aimed to give greater autonomy to Slavic regions within Austria-Hungary, but did not envision incorporating Bosnia and Herzegovina into Serbia. This policy was perceived by Serbian nationalists as a threat to Serbian unity and aspirations.