My MAC woes

I bought a MacBook, MacBook Air, and a Mac Pro. The Mac Pro froze half an hour ago, and I have no idea how to revive it. I was in mid-sentence in Firefox when it stopped working. It had installed some software updates a few minutes earlier. I got the “Force Quit” box up on screen, but it was non-functional. The Apple menu wouldn’t show its drop-down menu. Feeling helpless, I powered the system down. It rebooted to its frozen state. I have Skype onscreen. The control red, yellow, and green control lights look active when I run the cursor over them but I can’t click them. I have the Force Quit box on screen again. Skype is selected. Clicking “Force Quit” does nothing. The Mac Pro has become a big paperweight.