A Florida man has posted a picture of his murdered wife on his Facebook page along with a confession. Courtesy CBS

A SOUTH Florida man who allegedly killed his wife then posted a photo of her on Facebook has been charged with first-degree murder.

Miami-Dade police said in an arrest affidavit that Derek Medina, 31, said he shot Jennifer Alfonso, 26, at their South Miami home after she said she was "leaving him".

When officers responded to the home, they found Alfonso's body, as well as her 10-year-old daughter, who was unharmed.

According to the affidavit, Mr Medina said the couple became involved in a heated argument in an upstairs bedroom when he armed himself with a gun and pointed it at her.

He said Ms Alfonso left the bedroom, returning later to say she was leaving him. He says he went downstairs and confronted her in the kitchen, when she began punching him.

He claims he went back upstairs to get his gun and confronted her again, at which time she grabbed a knife. Mr Medina said he was able to disarm her and put the knife in a drawer, but that when she began punching him again, he shot her several times, the affidavit says.

A post on a Facebook page identified as Mr Medina's said at 11.11am on Thursday (1:11am AEST Friday), "Im going to prison or death sentence for killing my wife love you guys miss you guys takecare Facebook people you will see me in the news."

The post claimed that his wife was punching him and that he wasn't going to stand any more abuse. YouTube videos linked to his Facebook page earlier this week show him working out in a martial arts studio, punching and kicking a heavy bag.

The next and final post - also at 11.11am and titled "Rip Jennifer Alfonso" - was a gruesome photograph showing a woman in black leotards slumped on the floor. She looked like she had fallen backward, with her legs bent to her sides and blood on her left arm and left cheek. The photo was up for more than five hours before Facebook removed the page late on Thursday afternoon.

"The content was reported to us," a Facebook spokeswoman wrote. "We took action on the profile - removing the content and disabling the profile, and we reached out to law enforcement. We take action on all content that violates our terms, which are clearly laid out on our site."

Police declined comment on the Facebook posts.

Public records show that Mr Medina and Ms Alfonso first married in January 2010, divorced in February 2012 and then remarried three months later.

On his Facebook page, Mr Medina claimed to be a supervisor at a property management company and to have appeared in the Miami-based crime drama Burn Notice, though his name doesn't appear in online credits for the show.

Photos posted by Mr Medina on Wednesday show the family enjoying a meal alongside an unnamed marina and lounging beside a swimming pool.

Police said in the arrest affidavit that Mr Medina never called 911, only turning himself into police after going to see family and confessing.