You should probably interpret the incident as a rare fluke and try and forget about it. Murders and crime have happened on the AT before: Frequency of crime/assault on the Appalachian Trail
I have been accused of being overly paranoid Is it poor etiquette to ask fellow backpackers where they have been/where they are going? but I suggest you limit the info you share with strangers. You should also share your info with someone back home.
As you will be in the Whites on the AT, sign into the trail registers, talk to the hut care takers, and any thru hikers to get info about any problem people on the trail. They will readily share info if you just strike up a conversation. You can also check he thru hiker Facebook pages and the gut hook app for info about problems.
Details of the attack have now been released by the trek:
Jordan [the murderer] approached a group of Appalachian Trail hikers ... acting unstable. ... the group of hikers set up camp further along the trail... where Jordan appeared around 1am. He addressed the hikers through their tents, threatening to pour gasoline on their tents and set them on fire. As the four hikers decided to pack and leave the site, Jordan approached them, wielding a knife.
Two hikers fled the site northbound on the trail, placing a 911 call ... After giving chase, Jordan then returned to the site and confronted the remaining two hikers, Sanchez [the murdered victim] and an as-yet identified female hiker [the surviving victim]. After a verbal confrontation, Jordan began stabbing Sanchez, who fell to the ground. The female hiker fled the scene, pursued by Jordan who caught up to her and began stabbing her. The female hiker fell to the ground and played dead, at which point Jordan left the scene. The female hiker continued down the trail, finding help with a pair of hikers who assisted her six miles to Smyth County. They placed a 911 call ...
The full affidavit is also available. It seems like they did everything correct: camping as a group, moving own, calling 911 as quick as possible. Splitting up and the second group staying in camp, as opposed to leaving in the opposite direction immediately, was obviously the wrong decision in this case. That said, fleeing camp without gear is not the best choice in most circumstances either.