Q: my son passed away suddenly and we didn't want to turn off his comp as he had a password on it...we had someone reset passwords ...the comp worked fine until recently when we tried powering it up and now we get a gray screen with a message to turn it off

Sorry to hear about your son's passing.

If the gray screen has multiple messages in several languages telling you to turn it off, that's a kernel panic. A kernel panic is usually, but not always, caused by hardware, with memory the leading cause.

First unhook anything except keyboard and mouse that may be attached to the iMac and try to boot.  If that doesn't change anything, next reseat the memory. This Apple note tells you how to remove and reinstall the memory. And if that doesn't change anything, I would take it to an Apple store or AASP (Apple Authorized Service Provider) to look at it.