A 16-year-old boy has been arrested and charged with first-degree murder in the July 7 shooting deaths of his 15-year-old girlfriend and her 9-year-old brother at their Baltimore home.

Keith Maurice James Jr. is accused of killing Giovanna Myrie and Steve Allen. Court documents indicate that James Jr. had previously threatened Myrie, warning her he would kill her if she was unfaithful. "Keith said if I cheat he finna put the gun inside me. Help me," Myrie texted a friend days before the incident, according to charging documents obtained by the Baltimore Sun.

A friend told investigators that on July 4, Myrie and James Jr. FaceTimed with her from bed, and James Jr. was holding a gun during the call.

The suspect was expected to visit Myrie's home around 4 p.m. on the day of the shootings. Cellphone data and neighborhood surveillance footage reportedly placed James Jr. near the crime scene shortly after 4:20 p.m.

Myrie's mother discovered the bodies of her daughter and son, who had sustained multiple gunshot wounds, around 7:20 p.m.

Steve Allen was described by Baltimore County Police Chief Robert McCullough as an "innocent bystander."

James Jr. told police he had been dating Myrie for approximately two months but had not seen her in person since July 4. He was arrested on Tuesday and appeared in court on Thursday, where his attorney waived his bond hearing request. He remained silent during the proceedings.

"This case highlights for me a couple issues," McCullough stated, according to WBAL. "One is juvenile violence itself, violence by juveniles on other juveniles, and it also highlights the point that, as parents, we need to make sure that we know who our kids are associating with." He added, "It’s just dating violence, teen violence between people who have relationships, so we need to be mindful of those things."