Hostile Guild Takeover

A group of friends and I started a private guild together when we started playing the game. After a bit of time we began getting busy with work and other life situations. Logging back in I found a new member of the guild whom I never saw before. I began asking the group if any of them invited him, however none did. After a bit of time their item level sky rocketed and at the same time the game system stole the Guild Master position from one of my mates and transferred it to this random player which none of us knew. Today when doing my dailies I noticed he kicked everyone from the guild and began changing multiple things within it. We were all very excited to have our guild and traverse the world together however this has put a sour spot upon us. I am hopeful this can be resolved in some way as it is quite discouraging for such a hostile takeover. For reference the guilds name is Lazy Barrel.