What do Du think happened to Bolt's mom?

I Think she died

I think that she had Welpen and then they sent the Welpen out to different places, oder the Welpen in the same pet store could be bolt's bro's and sis's but just doesn't look like him. It is srtange that all of the Welpen look the same exepet for bolt, is it sapost to be the same breed? Bolt just could be white I guess but I think that only American shepards are white, mabey they are brown, I don't know, in the book and in the movie, they never told. None of the bolt facts tell either, so ask disney.