Miami-Dade police charged a 14-year-old South Miami Heights boy with the murder of his 11-year-old sister Monday, apparently after the two argued. The killing came just 10 days after the Department of Children and Families closed its investigation into a report that 14-year-old Ronald Eric Salazar had threatened to kill his entire family.

Ronald initially told detectives Monday morning that two men broke into his home and tried to rob the family, police said. He later confessed that he had killed his sister, Miami-Dade police spokeswoman Mary Walters said.

Marina Salazar's body was found a little after 8 a.m. Monday in a pool of blood in her bedroom at 11945 SW 173rd Ter. in South Miami Heights. She apparently had been strangled and her throat was cut, police said. Investigators were awaiting autopsy results.

Ronald, who will be 15 in September, was charged with first-degree murder.

On May 17, DCF's abuse hot line received a call about the family. A caller, whom The Herald could not identify, claimed that Ronald's father had been physically and verbally abusing the teen.

'VERY DEPRESSED'

''As a result of the verbal abuse, Ronald has been very depressed and two weeks ago he tried to kill himself by putting a knife up to his chest,'' the caller said.

The report said the father had been hitting Ronald with a belt and ``with his hands. . . . The father will come up behind Ronald and slap him.''

The boy told an investigator ''he didn't care if he lives or he dies.'' A sister told a caseworker Ronald ``marked up her neck by holding her down and choking her.''

''The child stated Ronald gets mad a lot, slams doors and hits people,'' a report says.

When Ronald became violent, the sister said, ''the family will normally start to pray.'' Even Ronald's parents were afraid of the boy, the report said.

In an interview July 13, Ronald's father told DCF Ronald said ''he will come back to the home and kill all of them'' if the state sent him to a residential program.

A DCF caseworker called police to report the family's fears and Ronald was committed to a locked psychiatric hospital for treatment that day. But a psychiatrist ruled he was not suicidal, and released him back to his parents.

Caseworkers closed their investigation of the Salazar family two days later, concluding that the children were not in harm's way. ''At this time, the risk of harm to the children is low,'' the report said.

Caseworkers did refer the Salazars to a private agency for voluntary services, but the family didn't keep an appointment with a counselor.

Flora Beal, DCF's Miami spokeswoman, declined to discuss the case Monday, citing privacy laws.

'VERY TRAGIC CASE'

''This is a very tragic case of sibling-on-sibling violence. Our hearts and prayers go out to the family during this troubling time,'' Beal said.

On Monday morning, the children's father, Samuel Salazar, left Ronald home alone with Marina and their 8-year-old brother while he took his 12-year-old daughter to school. The children's mother had already left for work, police said.

When Samuel Salazar came home he found Ronald in a neighbor's yard, police said. The teen had gone to the neighbor's house to call police after concocting the story about two men breaking into the house.

The teen told his father, ''We've been robbed, we've been robbed,'' said Miami-Dade Detective Alvaro Zabaleta.

The parents could not be reached for comment.

By midday, neighbors were questioning Ronald's story.

''It has to be somebody the family knows that did this,'' said neighbor Sandra Morris. "It can't be a stranger.''

School officials were distraught to learn they lost such an apparently happy student.

''Marina was an exceptional little girl,'' said Lola Johnson, who was the girl's fifth-grade teacher last year at Miami Heights Elementary. "She was just a flower, she was just lovely.''

In most ways, she was a typically loveable fifth-grader: she wrote poetry about nature and read stories.

But she never mentioned her siblings. ''She never talked about them,'' Johnson said.