2013 Ram 1500 Wouldn't Accelerate, Won't Restart

I was driving my 2013 Ram 1500 (5.7) on a two-hour road trip, and for the first
hour and 15 minutes, everything was fine. No weird engine noises, no
shaking, no display issues, nothing. I was approaching a red light, and I had
my cruise control on but not set, and as soon as I started braking, the cruise
control turned itself off and wouldn't turn back on. I stopped at a red light,
and my truck was still running, not making any odd noises or anything. Once
the light turned green, I tried to accelerate and nothing happened. I tried a
couple more times, still nothing. I turned the truck off in an attempt to restart
it, and it wouldn't turn back on. The engine wasn't turning over when I tried
to crank it, all you could hear was a whining/clicking noise. It hasn't run
since, and the mechanic says it's a cylinder issue, but I'm not so sure. Need
opinions on this! The truck has 116k miles on it and has never had any
kind of mechanical trouble before and has been serviced regularly.