why cmake pick the wrong library?

I have this line in my cmake to pick glog library:

find_library(GLOG_LIBRARY libglog $ENV{GLOG_DIR}/x64/Release)
message(${GLOG_LIBRARY})

and in the release folder I have these files:

03/03/2015  15:00           308,736 libglog.dll
03/03/2015  15:00            64,998 libglog.exp
03/03/2015  15:00           104,884 libglog.lib
03/03/2015  15:00         3,248,128 libglog.pdb

But when I run cmake, I can see that GLOG_LIBRARY is set to libglog_static.lib

why cmake get the wrong library?