LAKE CITY, Fla. -

A 25-year-old Columbia County man sentenced to probation on Monday is arrested early Thursday morning, accused of killing his girlfriend, another woman and a man.

Hours after deputies found three people dead in a Lake City home, deputies arrested Alan Lucas Strattan, who called in the crime. He was charged with three counts of first-degree murder.

Sheriff's Office investigators discovered two women and one man apparently shot to death in a home off the 1500 block of Southeast Baya Drive about midnight. Sheriff Mark Hunter identified the victims as Monica Hudson, 27, Michael Tucker, 32, and Nichole Cervantez, 25.

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Hunter said Strattan went to the Lake City Police Department about midnight to tell them he had killed three people inside his parents' home. He was taken into custody without incident and booked into the Columbia County Jail without bond.

Hunter said a 5-year-old girl in the house at the time of the homicides and was with Strattan when he turned himself in. The girl, who is Cervantez' daughter, was unhurt and is being cared for her by her grandparents.

Detectives said they weren't sure yet if the girl witnessed her mother's killing or if she saw the aftermath.

"I think she came downstairs and actually saw it because of her reaction to the questions the deputy asked her," Dustin Bass, Hudson's stepfather and the girl's step-grandfather, said.

Authorities also said Cervantez was six months pregnant when she was killed.

Hudson was Strattan's girlfriend and was friends with the other two victims. Hunter said there was apparently an argument prior to the shootings, but he didn't know the nature of it.

Channel 4 learned that Strattan was placed on one-year probation on Monday for a misdemeanor battery conviction. Hudson said his deputies were very familiar with Strattan, but would not elaborate.

"How does it get to this point? How can someone with that many domestic violence charges be free," Bass said of Strattan.

Bass said he warned his daughter about Strattan multiple times.

"I have pictures of the beatings she took from him," Bass said. "I don't understand the logic of her going back to him so many times."

Detectives and crime scene investigators spent the night gathering evidence at the home and said the gun likely used in the killings was recovered. The medical examiner's office in Jacksonville was to conduct autopsies to confirm the cause of the deaths and the Florida Department of Law Enforcement was assisting with processing evidence.

Hunter said a triple homicide comes as a shock in Columbia County, which had only one killing in 2010.