how to kill a yum lock?

[Nathan Huang]

Hi guys
after waiting for yum programme a long time, I type Ctrl+c to turn back 
to command line. but when I try yum command second time,
I was informed that the previous programm are still hold yum, and 
working background.
I try to kill the process by suing kill 3282(pid). but it doesn't work
who can tell me how to kill a process in proper way.
thanks in advance
nathan