How to terminate multiple applications via Activity Monitor
I would suggest you to:


Launch Terminal
When Terminal has launched, type "top" into the Terminal window. You'll see a list of currently running processes. At the top of the list is an overview of the processes that are running and the resources they're consuming.
When you identify a process that's causing a problem or consuming too many resources, take note of the number in the PID column next to the name of the process. To kill the process, type "kill -9" followed by the PID number. Press Enter. The problem process will now quit.