The logging system in JBoss catches both stdout and stderr and sends them to the configured logging appender. By default the logging system logs to both the logfile and stdout and that why you find your stderr output in the stdout.
All System log, JBoss logger and JDK Logger are redirected into D:\java\jboss-as-7.2.0.Final\standalone\log\server.log
If you are new to jboss as. you can read some books about it.