why did my suburban die and now won't crank?

I have a question about my 2009 Suburban. I was driving out my driveway
today (4 miles long) and at about 2 miles it started to hesitate just a bit, kinda
like the tranny was slipping or like it was out of fuel. I kept going because it
stopped doing it and then at 3 miles it just died. It kinda acted like it was out of
fuel, which made me think fuel pump. But then I turned the key off and went to
try to turn it over and it does absolutely nothing. Lights and radio work, but
there is no starter clicking or any noise at all. I walked a mile back to cell
service with my baby on my hip and called my husband and he came and
picked me up. we loaded the Suburban onto a flatbed and hauled it to our
mechanic. I don't want to throw parts at this issue but we're pretty stumped as
to what the problem may be. Any ideas?