pit bull?

From Reader Digest:

Our daughter's condo was the target of a break-in. The following morning in church, one of her girlfriends came running to her, gave her a big hug, then told her,"you need to either get married or get yourself a pit bull." 
A middle-aged usher offered his advice:" get the pit bull!"

Pit bull--是狗吗？查字典是rapper, rapper 又不是狗？
为什么用the following morning? 从没用过，什么情况下用？
为什么用came running to her? 要我肯定用run to her?
usher是谁？

thank you