No, that's not how that felony part of citizen's arrest works, as per your own sourced law code:
If he isn't escaping from said felony, then you don't get to arrest him. Basically, if you happen upon seeing a guy who's face perfectly matches a description for a murder suspect, you can't actually citizen's arrest him because he isn't currently escaping.A private person may arrest an offender if the offense is committed in his presence or within his immediate knowledge. If the offense is a felony and the offender is escaping or attempting to escape, a private person may arrest him upon reasonable and probable grounds of suspicion.
But you're right, the statute could be read in a way even worse for McMichaels.
Reading it a second time, the offense seems to have to have existed for probable cause to matter. So for example, if I secretly rob a bank, and walk funny, and a guy has a reasonable suspicion of me (but not probable cause) and citizen's arrests me, that's not a legal citizens arrest because he didn't have probable cause. But if I didn't rob a bank, but looked like I did past probable cause, since there is no offense committed, I could see that not being a legal citizen's arrest either. It's an if then clause, and if there is no felony, then you can't get to the then clause.
The other way to look at it, and it seems that a number of georgia lawyers that are quoted say this, is that the offense has to happen in your immediate knowledge. Basically, they are saying that the two bold words are linked:
Personally, I'm not so sure about this reading, but it seems to be a consensus among all the lawyer sources I see.A private person may arrest an offender if the offense is committed in his presence or within his immediate knowledge. If the offense is a felony and the offender is escaping or attempting to escape, a private person may arrest him upon reasonable and probable grounds of suspicion.
Regardless, and more importantly, I think I found some insight into the strategy of the prosecutors:
First, read this ConcealedCarry.com article from 2009:
When Does Citizens Arrest Become Aggravated Assault » Concealed Carry Inc
The little things that we do often get us into trouble. While the laws do vary from state to state, and clearly I'm generalizing here, the primary difference between armed citizens and law enforcement is our inability to...
www.concealedcarry.com
Then recall that the two charges that made it through grand jury are aggravated assault and felony murder. This dodges the citizen's arrest statute, I'm pretty sure. I've updated the legal definitions above with what assault and aggravated assualt are. This makes a much tighter case than what I was hypothesizing. Basically, making Arbery fear for his life is a crime, which is aggravated by doing it with a gun. This is a felony, and felony murder follows.