A South Miami man has been charged with first-degree murder after authorities say he confessed to fatally shooting his wife and posting a photo of her body on Facebook.

Police said they discovered Jennifer Alfonso, 26, inside a townhouse in the 5500 block of Southwest 67th Avenue after Derek Medina, 31, showed up at the station and said he killed his wife after a domestic argument.

When officials arrived on the scene, they found Alfonso dead on the kitchen floor suffering from multiple gunshot wounds, said a Miami-Dade arrest report.

A 10-year-old child was also found unharmed at the scene. Miami-Dade Police said the child was Alfonso's daughter. Police confirmed the child was home during the murder but haven't said if she witnessed it.

Medina told officials he had gotten into a fight with Alfonso at about 10 a.m. Thursday, the arrest report said. He was in his bedroom when he grabbed a gun from his closet and pointed it at Alfonso, so she left the bedroom, but came back later to say she was leaving him, the report said.

See original report at NBCMiami.com

She went down into the kitchen and Medina followed her without the gun, but Alfonso began to punch him, so he went back to get his firearm, according to the report.

Once he was downstairs with the gun, Alfonso grabbed a knife, but Medina was able to take it from her, officials said.

Alfonso began punching him again and that's when Medina shot at her, the report said.

After the shooting, Medina posted a photo of his wife on his Facebook page. The graphic photo, captioned "RIP Jennifer Alfonso," shows a woman slumped on the floor, on her back with her legs bent backward and blood on her left arm and cheek.

He also posted the following comment shortly after posting the photo:

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" my wife was punching me and I am not going to stand anymore with the abuse so I did what I did I hope u understand me

At some point later, Medina changed his clothes and left the scene without calling 911, police said. He then went to family members, confessing what he had done, before turning himself in to police, according to the report.

Neighbor Yoshi Dade said Medina was a self-proclaimed neighborhood watchman.

"He walks around with a concealed gun, so he tries to be the neighborhood watchguy. He's always there late night and he's weird to me he's always kind of looking around and trying to be a hero," Dade said.

South Miami Police said the case was being handed over to Miami-Dade Police.

Family and friends of Alfonso showed up at the scene and said the couple met at Denny's, where she worked, and that he had actually written several books dedicated to her. One them titled: "How I saved someone's life and marriage and family problems thru communication."

The photo was up for more than five hours before Facebook removed the page late Thursday afternoon.

A Facebook spokeswoman said in an email to The Associated Press that she couldn't comment on a law enforcement investigation but could provide a general comment from the company.

"The content was reported to us," the 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."

Public records show that Medina and Alfonso first married in January 2010, divorced in February 2012 and then remarried three months later. Medina bought the condominium unit where the couple lived in March 2012 for $107,000.