my cocker spaniel

Has been being harassed by my "big dogs" and for two days now he has been on a "line" by the house, and the other two have remained in the pen. This is where he used to be all the time, before we got the huge pen. (And by huge I mean, I could park several cars inside it.)
We always let him off the line to play when we are out. He is a car chaser, so it is his own fault that he is confined at all. Well, today, he bit BOTH my kids and attempted to bite me. Karsyn was pulling the chain to untangle him and I let that "nip" go because I thought she accidentally hurt him, and it was not a bad bite, just one that made me very mad.

After that, he got into the empty box I had by the back door, and I told Jordan to take it. He jumped up and tried to bite her head, and got a mouthful of hair. It's pretty likely that if my neighbors saw me punish him, that they then called PETA. I don't know what is up with him, but he is back in the pen. I don't care if they kick him around or not, he isn't taking out frustration on my kids. He growled at me like a psycho when I approached him, but ran back into the pen like he wanted to be there, so who knows....