2005 Chrysler Pacifica backend swerving

I just got this 2005 Pacifica and when I test drove it, it was a nice smooth drive and they replaced a tire and did a wheel alighnment and when I drove it home I noticed the backend swerved very easily and then my husband drove and almost rolled it because of it swerving at the back end. The new tire that was replaced was at the back end. And also when you brake it swerves to the left at the back end.