how to kill this process

[snnn]

# killall -CONT mysqld
# killall -CONT mysqld
# ps -A|grep mysqld
72:39951  p0- T      0:01.21 /usr/local/libexec/mysqld
--defaults-extra-file=/var/
176:25582  p1  R+     0:00.00 grep -n --color=auto mysqld
# kill -CONT 39951
# kill -9 39951

I cannot kill it by "kill -9"
why?

This the my environment
bbs# uname -a
FreeBSD bbs.xxx.edu.cn 5.4-RELEASE-p12 FreeBSD 5.4-RELEASE-p12 #2: Thu Mar
16 1
5:48:16 CST 2006     root at bbs.xxx.edu.cn:/usr/obj/usr/src/sys/MYKERNEL  i386