‘It was a mistake’: Man, 19, confesses to fatally shooting 14-year-old sister in Opa-locka

Amid tragedy, parents believe fatal shooting was accidental

OPA-LOCKA, Fla. – A father cried on Thursday in Miami-Dade County near his front door, which had a sign that read, “Love Lives Here.”

Detectives had arrested his 19-year-old son for shooting his 14-year-old daughter at the family’s Opa-locka townhome. Police identified the suspect as Keon Martavious Thornhill.

The grieving parents identified the victim as Briana and said they believe the shooting was accidental.

“I shot her! It was a mistake. Take me in,” Thornhill told police officers, according to the arrest report.

Briana suffered a gunshot wound to the face at the townhome in the gated community of the Mirage at Sailboat Cove near the intersection of Northwest 143rd Street and 17th Avenue, according to the arrest report.

Police officers responded to Thornhill’s family townhome after neighbors called 911 to report that there was a man knocking on doors, asking for help at about 3 a.m., according to the report.

Thornhill allegedly told a neighbor, who is a police officer with the Opa-locka Police Department and who was off duty, that his sister was injured. Miami-Dade Fire Rescue personnel pronounced the teenage girl dead at the home.

Thornill first told police officers that he had gotten into an argument with his sister and he had handed her his gun and she had shot herself, according to the report.

Miami-Dade detectives first detained Thornhill for questioning at the headquarters in Doral where he provided inconsistent statements after his initial confession, police said.

This is a mug shot of Keon Martavious Thornhill taken when police officers arrested him in July 2022 for grand theft auto. (MDCR)

“There were four additional siblings inside at the time of the shooting,” said Detective Alvaro Zabaleta, a spokesman for the Miami-Dade Police Department.

Thornhill, his sister, and the four other children, whose ages ranged from 9 to 12 years old, were home alone since their parents were at work, according to Zabaleta. The four were not injured.

“Detectives have also spoken with the family members who said they had no idea there was a firearm inside of the house,” Zabaleta said.

Records show police officers arrested Thornhill in July 2022 for grand theft auto. He is facing a second-degree murder charge.


Watch the 4 p.m. report

Watch the 12 p.m. report

About the Authors:

Roy Ramos joined the Local 10 News team in 2018. Roy is a South Florida native who grew up in Florida City. He attended Christopher Columbus High School, Homestead Senior High School and graduated from St. Thomas University.

The Emmy Award-winning journalist joined the Local 10 News team in 2013. She wrote for the Miami Herald for more than 9 years and won a Green Eyeshade Award.