<human>: I met my friend's husband before they got married a few years ago, and thought he was a pretty awesome guy. We got along, have a similar sense of humor and generally I enjoy spending time with them. 

The problem is recently, he's been sending messages with sexually explicit content, like what he's done with previous partners, what's lacking in his marriage and just stuff I would never expect from a friend's husband.

I'll admit I initially awkwardly laughed it off, since I was uncomfortable and didn't know how to respond. So it kind of snowballed until I finally asked if my friend was aware of what he wrote. He claimed she was, and I figured at least I put it out there that I wasn't okay with what was going on, and have never implied I was interested in him in any way. 

It seemed to get better but he's sent pornographic images of women and made comments like "I really like her 😺" (not with a smiley) so I've stopped replying and don't know if I should get my friend involved at this point. Sorry if it seems like there's an obvious solution and I'm being stupid, but i just don't know what to do in this case. Any help would be appreciated.

Could you distill the essence of the text into 1-3 sentences?
<bot>: Friend's husband has started sending sexual messages about his past experiences and graphic photos (not of him), I'm not sure if friend should be informed of what's happening or did there's a way to stop this without causing problems.