Trump's Self-centernedness

Who would make a statement like this:

http://www.npr.org/sections/thetwo-way/2016/01/23/464129029/donald-trump-i-could-shoot-somebody-and-i-wouldnt-lose-any-voters

and why would anyone support such a person, let alone a presidential candidate?

How could such a person have the best interests of America in their heart?