can't foreground job (Suspended (tty input))

[Michael ODonnell]

sudo will have executed the setuid(0) syscall and then exec'd
emacs, which consequently runs as a privileged process rather
than retaining your credentials - the whole point of using
sudo in the first place.

That "sudo kill %1" fails because that % notation only makes
sense in the context of the shell's internal job control
machinery, but when you say "sudo someProg" then someProg is
required to be an executable somewhere in your $PATH, which in
your case is probably /bin/kill, to whom that "%1" notation
makes no sense because it has no idea which processes were
spawned by your shell.  When you invoke /bin/kill (rather than
the shell's builtin "kill") you need to specify actual PIDs.