My parents computer ended up infected with that "your computer has a virus call here to resolve the issue" web pop ups scams. They ended up calling and during the process, obviously, granted the hacker remote control over their computer. Luckily they didn't pay any money, they also never logged in to any account or anything while the scammer had control or anything. The computer is also connected to their home wifi which has other devices.

Parents turned off the computer already, and just wondering what the next steps to do are? Is the computer still safe to use? Do they have to buy a new one? What about the other devices on their home network, do they have to be changed?