What is the specification of his computer? The anti-virus software should be appropriate to his computer. If he is running a low specification of computer then he must use Avira. Kaspersky is also a good anti-virus for high specification of computer.
That's really a strange activity of your computer. If the safe mode and scanning process of your anti-virus didn't work, you need to run the restoration. Restore it even the last file before you encounter this.