pgrep strangeness

See the picture below. Why it print PID found 3 times?
Is it because too many 'sentinel's in the command line?
It looks like some analog of 'sort -u' should be performed (qsort(3)?)

# pgrep sentinel
547
547
547
# ps ax | grep sentinel
  547  ??  Ss     7:48,83 /usr/local/sbin/sentinel -v1 -c /usr/local/etc/sentinel

-- 
Andrey Chernov | http://ache.pp.ru/