North Hollywood man admits to fatally stabbing sister, police say

Los Angeles homicide detectives continued their investigation Thursday into what motivated a North Hollywood man to allegedly chase down his sister and stab her to death in front of their parents.

Mario Alejandro Martinez, 22, was being held in lieu of $1-million bail on a murder charge in the Monday night killing of his 19-year-old sister, Raquel Martinez.

It was an “extremely brutal attack,” said LAPD Det. Thomas Townsend and marked the bloody conclusion of months of unexplained hostility the elder Martinez had toward his younger sister.

Mario Martinez was convicted of battering his sister in February and was on probation for that conviction when he allegedly killed her Monday, Townsend said.

The encounter started about 6:45 p.m., when Raquel Martinez stopped by her parents’ house in the 6000 block of Farmdale Avenue in North Hollywood to drop off formula for a niece or nephew.

The 19-year-old was either just outside the front door or had just walked through the threshold when Mario Martinez heard his sister’s voice, Townsend said.

Martinez “heard her and retrieved a knife from the kitchen and chased her and attacked her on the sidewalk,” Townsend said.

Their mother’s screams alerted their father, who ran outside and found Martinez on top of his sister, stabbing her, police said. Neighbors who heard the screaming called 911 while Martinez’s father disarmed his son and kept the knife for police, Townsend said.

Witnesses also “stepped up and did the right thing” and followed Martinez as he fled, Townsend said. Martinez was caught by police, who recognized him by the description given by witnesses who followed him while talking to dispatchers.

Martinez eventually confessed to killing his sister while in custody, Townsend said. Police have not yet determined a motive.

The 2-year-old toddler that Raquel Martinez was dropping off formula for was also at the scene and witnessed the incident, police said. The child belongs to a third Martinez sibling, Townsend said.

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Joseph.serna@latimes.com

@josephserna