It sounds like (at worst) he put himself on Facebook showing gang signs. This is stupid, but not always malicious. Then the actual gang committed a murder. So now they are going to charge him with benefiting from the murder.
If this is all that exists, how this can possibly pass the “beyond a reasonable doubt” criterion is beyond my ken.
I agree. We don't know for sure, but if your characterization of what happened is true, then this is BS and the true perps are the "law enforcement" officers.