Solaris, grant user to kill another process

the task is grant user1 to kill another (for example user2) process. My steps:
by root:

usermod -P "Process Management" user1
login user1
user1@server (~) pfexec kill <PID>

the result is:
k

sh: <PID>:  not found

or

user1@server (~) pfexec pkill <PID>

the result: nothing happens, still user2 process in ps -ef

user1, user2 default shell /usr/bin/bash

What's is the problem?

------ Post updated 07-20-18 at 02:59 PM ------

Problem is solved:

Someone change the permission on /usr/bin/kill ( -r-sr-xr-x 17 root bin 134 Jan 22 2005 kill )

Should be: -r-xr-xr-x 1 root root 134 Jan 19 2018 kill