What is wrong with people?

Here is a story from suburban Detroit that just makes me sick. What is wrong with people?

From the Fox affiliate in Detroit, WJBK:
"Parents: Dying Girl, 7, Taunted by Neighbors in Trenton"
http://www.myfoxdetroit.com/dpp/news/the_edge/dying-girl-taunted-by-neighbors-in-trenton

From the story:
"A member of Kathleen's family says the bad blood started about two-years ago after the two families had a falling out over a birthday party at the Rose house. At the party, kids were using a 'bounce-house' and playing games in the front yard. The source says that Jennifer Petkov texted someone in the Rose family, asking if her kids could come to the event. A response to the text did not come quickly enough and it angered Jennifer. According to the Rose family, she's been harassing them ever since."

My first reaction is that we can't assume that this is true, or that it is the whole truth. It may just be one side of the story. But if this was the root of the bad blood, I have to ask once again: What is wrong with people?