Not surprising. One of the striking things about the police report was how candid Greg McMichael was about the fact that this was a pursuit, featuring not one but two vehicles and at least two separate attempts to cut Arbery off in the street. Arbery didn’t chance upon them while he was running and stumble into a confrontation. They went after him, fully armed.
That’s how confident McMichael was that he and his son wouldn’t be punished for killing Arbery. He admitted the pursuit to the police.
The most defensible scenario for a citizen’s arrest is when a crime is committed right in front of the person making the arrest, to the point where they’re practically a part of it. I’ve used the example before of bank robbery: If the man in line in front of you pulls a gun on the teller and you jump him and hold him until the cops come, we don’t want you to suffer any criminal jeopardy for that. It’s not just because you’ve done a good deed by apprehending a dangerous person whom we know is guilty. It’s because that crime was thrust upon you. You were in danger. If you had run, you might have been shot. Instead you did what you could to protect yourself and the other people there. Looked at that way, a valid citizen’s arrest is a cousin of self-defense.