how to kill all process owned by a user?

[Jianping Zhu]

Lot of process owned by user colin, they used lot of cpu space, how can
I kill all of them?
THX



PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME CPU COMMAND
 1858 colin     22   0  1568 1568  1300 S     6.9  0.4   0:01   0
 openssl
  1373 colin     15   0  1072 1072   936 S     1.9  0.2   0:08   0 atac
  1374 colin     15   0  1072 1072   936 S     1.5  0.2   0:06   0 atac
  1462 colin     15   0  1068 1068   936 S     1.5  0.2   0:07   0 atac
  1475 colin     15   0  1072 1072   936 S     1.5  0.2   0:07   0 atac
  1652 colin     15   0  1104 1104   972 S     1.1  0.2   0:03   0 atac
  1169 colin     15   0   520  520   432 S     0.9  0.1   0:04   0
                                                                ssh-scan
  1392 colin     16   0  1104 1104   972 S     0.9  0.2   0:04   0
      atac
  1396 colin     15   0  1104 1104   972 S     0.9  0.2   0:03   0
       atac
  1403 colin     15   0  1104 1104   972 S     0.9  0.2   0:04   0
	atac
  1653 colin     15   0  1104 1104   972 S     0.9  0.2   0:04
	 0 ata
1654 colin     15   0  1104 1104   972 S     0.9  0.2   0:03
	  0 atac
	   1656 colin     15   0  1104 1104   972 S     0.9  0.2   0:04
	   0 atac
	    1167 colin     15   0   520  520   432 S     0.7  0.1   0:02
	    0 ssh-scan
	     1171 colin     15   0   560  560   476 S     0.7  0.1
	     0:01   0 ssh-scan