Ungrounded outlet - tenant request

[Mike H.]

Hello BP community, 

Need some advice. 

Facts : outlets in house are mostly ungrounded two prong. One outlet has three prongs but also ungrounded. Location Florida. Tenants have renters insurance. 

Tenant says he plugged surge protector in the 3 prong outlet thinking it was grounded. Says there was a power surge that fried his computer and wants me to give him full replacement cost. It's a significant amount. In my 15 years of managing these couple rental properties I own I've never run into this situation. 

I tend to think that I'm not responsible. I think renters insurance should cover. But also wondering about the 3 prong outlet that's not grounded. I also want to do the right thing. 

Thanks!