Bug, Synth or alternate questline?

First off I spent a lot of time with Minutemen before joining the Railroad. I'm their General. And Preston never leaves Sanctuary except that one time to retake the Castle.

So I left Greentop with Curie heading south on the road. Saw a person shooting a raider. Went up to him and it was Preston. He said " Hi, I don't think we've met. I'm Preston Garvey." I killed the raider, turned back around and Curie and Preston were going at it. Poor Preston didn't stand a chance since I had Curie fitted with the Grognak gear. She actually killed him, lol.

i finally thought I was free of those damn missions for good but had to check Sanctuary to be sure. Damned Preston was there. Waiting with a mission.

Anyone know what's going on?

He's a fake, a con-man.
Run through his dialogue for some lols.

Take a look on youtube for other folks vids of him too.

Ok, thanks. I'll have to YouTube him since Curie hacked him to death.

Not sure why Curie went off on him - even after you expose him ("No, seriously, ~I~ am the General") he just runs away.

Ah I just ran into this impostor the other night and I was going to make a thread about it. I hadn't heard from anyone else about running into him. I'm like "Lol this isn't Preston, this is a poor man's version of Preston." So he's a Con-man huh? Wasn't sure if he was a Synth or Impostor or what but i let him live, it was just too funny watching him run off.