While we wait for answers, these related questions may interest you:
No. The actions of Gavrilo Princip in assassinating the Archduke Franz Ferdinand did not "single-handedly" start the First World War. Instead, the actions of Princip can be considered a "match which lit the tinderbox" to use a phrase historians throughout the decades have repeatedly asserted. The First World War could not have started simply due to the assassination of the Austro-Hungarian Archduke, and it remains a question of great historiographical interest. To quote an earlier Saturday Showcase of mine on a related matter:
"When shots rang out in Sarajevo and killed the heir apparent to the Austro-Hungarian throne, they rang out in a world beset with a litany of factors which, despite none of them being a key casus belli, presented the leaders of Europe with a geopolitical situation where much was at stake. The militaristic war plans and naval arms race were not turned to as the first option; though the decision to call forth the reserves and pack the troop trains was one which helped the dominoes to fall quicker than they might have had in previous years, but they alone cannot explain how an entire continent marched off to the front."
The following writeups from my end should be of some interest to you as further reading in addition to u/Sjoerder's linkdrops: