Oh it was definitely planned. The person filming was part of the hunting posse and is currently being investigated. The video leaked after they passed it around online among their neanderthal crew like memorabilia. This is a good example of how anything posted online can and mostly likely will eventually leak to the general public.
It wasn't some innocent bystander filming, it was a participant.
If you videotaped your friend killing someone, is the video getting out? Yes I know it was a guy involved who recorded it.
Edit:
This is how the video got out.
The video — which by Friday officials had described as “a very important piece” of evidence in moving forward with criminal charges — was first posted by WGIG, a local radio station in Brunswick, Ga., which said it had obtained the footage from an anonymous source.
But in a twist emblematic of the small-town politics that have defined the case, that source turned out to be a criminal defense lawyer in town who had informally consulted with the suspects.
The lawyer, Alan Tucker, said in an interview on Friday that the video had come from the cellphone of a man who had filmed the episode and that he later gave the footage to the radio station. Mr. Tucker’s role was confirmed by Scott Ryfun, who oversees the station’s programming.
Asked why he had leaked the video, Mr. Tucker said he had wanted to dispel rumors that he said had fueled tension in the community. “It wasn’t two men with a Confederate flag in the back of a truck going down the road and shooting a jogger in the back,” Mr. Tucker said.
“It got the truth out there as to what you could see,” he added. “My purpose was not to exonerate them or convict them.”
https://www.nytimes.com/2020/05/08/us/ahmaud-arbery-video-lawyer.amp.html