"Porphyria's Lover"

When reading "Porphyrai's Lover" by Robert Browning, I thought it was going to be about a man and a woman engaging in an intimate moment and that was it. But as I got further into the poem I could tell it was actually about a man who kills his lover. "Too weak, for all her heart's endeavour,/ To set its struggling passion free/ from pride, and vainer ties dissever,/ And give herself to me for ever"(lines 21-24). I feel that these lines were the turning point in the poem, he knew she loved him and wanted to be with him and he did not want to lose her so he killed her so she will be with him forever. He said "That moment she was mine, mine, fair,/ perfectly pure and good: I found/ A thing to do , and all her hair/ In one long yellow string I wound/ Three times her little throat around,/ And strangled her. No pain felt she;"(36-41). He strangled her with her own hair and seemed not have no emotions about killing her, no remorse. He almost seemed to try and validate why it had to be done, so she couldn't leave him and had to be with him for ever. It's a very dark poem but definately an attention grabber, it kept my attention.