A young father shot dead the teenage mother of his son then turned the gun on himself in front of police on Thursday.

Kai Williams, 20, killed 18-year-old Larissa Barros at her family's home in Poinciana, Florida. She was two weeks away from graduating from Liberty High School and had been accepted in to Florida State University.

Williams, who was previously jailed for stalking and had been ordered to stay away from the teenager, then took his own life two blocks away when police, who she had called to the scene before she died, approached him.

Barros called 911 at 12.05pm to report that someone she knew was trying to break in and that he was armed.

Larissa Barros, 18, was murdered by her ex-boyfriend Kai Williams, 20, who turned the gun on himself when police approached him after the killing

By the time officers arrived in the neighborhood, Williams had fled the house and was two blocks away.

When the responding officers attempted to approach him, he shot himself in front of them.

The officers then discovered Barros's body in her home. There was no one else in the house at the time.

Previous court records show that the pair had a tumultuous relationship and that Barros was afraid of her ex.

She requested a permanent domestic violent injunction against him last year after telling a court that she was afraid he would harm her or their young son.

'For almost two years, my life has been made miserable by Kai Williams. Kai has been unstable and jealous.

'I am afraid he will hurt me or my child if he gets the opportunity,' she said in the most recent request which was viewed by The Orlando Sentinel.

Barros previously told authorities she was afraid Williams would hurt her or their 15-month-old son

Barros had taken out two domestic violence injunctions against her ex and he spent time in jail for aggravated stalking

Police discovered the teenage mother's body in her home in Poinciana, Florida, on Thursday afternoon

In September, the 20-year-old slashed the tires of her car in the parking lot of her high school. Days later, he set the vehicle on fire.

He spent less than two weeks in county jail before being released.

The injunction was granted afterwards.

In December, Williams was arrested again for violating it by trying to contact the high school student.

He returned to county jail but was released on January 12. Barros made no reports that he had tried to contact her since then before her death on Thursday.

Friends paid tribute to the 18-year-old in light of the tragedy, describing her as a motivated young mother who was determined to go to college.

'She was beautiful and smart. She loved her son more than anything and would have done anything for him.

'A beautiful baby boy will grow up without of his parents now,' said one.