A 15-year-old boy is accused of shooting and killing his ex-girlfriend's mother and her two siblings at a home in west Texas, police said.

Odessa police said they responded to a shooting at an apartment around 5:45 p.m. on Tuesday. Officers who first arrived at the residence found three people dead inside the home. A 15-year-old suspect fled the scene but was located about 40 minutes later, Police Chief Mike Gerke told local media.

At the time, Gerke said the shooting was intentional and targeted the three victims, according to CBS affiliate KOSA-TV.

The investigation into the shooting revealed that the 15-year-old boy had planned on shooting his ex-girlfriend outside of school but changed his mind and instead went to her home, police said.

There, the suspect entered the home and shot his ex-girlfriend's mother, identified as 39-year-old Jessica Rodriguez, police said.

The teenager then shot his ex-girlfriend's 9-year-old brother and 13-year-old sister.

At a news conference on Wednesday, Gerke called the shooting a "tragic and cowardly act of violence."

Gerke  declined to say whether the 15-year-old ex-girlfriend was home at the time of the shooting. He did say she was not physically harmed.

"She is OK, she wasn't injured … I'm sure after all this happened to her family, she's not OK. But physically she was unharmed," he said.

Gerke said the shooting and the circumstances surrounding it are still under investigation. He did not elaborate on any motive.

The 15-year-old, who has not been identified, was charged with capital murder of multiple persons. He is currently in the custody of the Ector County Youth Center.