As in your previous loglines, most of what you have here is setting. Only at the end do we find...
It seems to me the situation is timeless. It could be set anywhere at any time. Why select the summer of love? (Which entails a bigger budget for time period props, costumes and location dressing.)
Story is conflict What is the main conflict?
It sounds as though the inciting incident is when a serial killer falls in love, but what is he going to do about it? What is his goal as a result of falling in love?
I’d say we need to state the goal up front.
After falling in love with his next victim a serial killer uses his new feeling to try and defeat his dark urges.
Does she know? Is he doing a 12 step program? Is there flavour we can add.