Heartbroken aunt mourns 4-year-old nephew but supports brother on trial for his child's killing in Baltimore County

Jurors saw pictures of blood-stained walls and the gun prosecutors allege a Maryland father used to kill his young son and shoot his infant daughter. They also heard Thursday from the lead detective who investigated the high-profile Baltimore County murder case. 

Mark Jones Jr. faces life in prison if convicted of murder and attempted murder. Police said he also shot the children's mother before shooting himself on Christmas Eve 2024 inside a Rosedale apartment. 

Defendant's sister speaks 

Jones' older sister Cierra spoke to WJZ Investigates after hearing days of emotional testimony. 

She said she is still reeling from the death of her four-year-old nephew Jacobi, while also standing by her brother.

"I'm keeping my nephew Jacobi's name alive,  and I'm here by my brother's side," she said. "Jacobi is living in us every day. That's my only nephew."

Her brother's defense claimed the children's mother pulled the trigger—not him. Jones' attorneys have questioned the thoroughness of the investigation and said police automatically blamed Jones for the killing, arguing there was a struggle for the gun. 

The defendant's sister said the killing has torn her family apart, and she is not worried about people judging her brother or her support of him. 

"They can judge all they want. Everyone knows who Mark was. Everybody knows who he is," his sister said. "That's all that matters."

Prosecutors push back 

Prosecutors alleged Jones refused to leave the Rosedale apartment after hours of arguing with the children's mother, Promyss Marcelle, and was enraged about custody arrangements and child support issues, so he shot and killed Jacobi and his one-year-old daughter Peyton and their mother Marcelle before turning the gun on himself.

The semiautomatic pistol used in the crime was registered to Jones. Jacobi was shot in the middle of his forehead.

Detective Mark Fisher took the witness stand Thursday and said the evidence pointed to the defendant's guilt. 

Fisher said there was "no corroborating evidence from witnesses" that supported the defense's assertion that Marcelle pulled the trigger. 

Deputy Baltimore County State's Attorney Lisa Dever asked Detective Fisher if anything he heard in court from the defense Thursday changed his opinion. 

"No," Fisher responded. 

Public Defender James Dills told Fisher, "You decided what information to look at. You decided what information to ignore."

Hospital video 

Dills objected to jurors seeing police body camera video of Detective Fisher asking Jones questions from his Johns Hopkins Hospital bed. 

The judge ended up allowing jurors to watch it.

Jones communicated using a whiteboard because he was still intubated after the shooting. 

"I've never seen it where a person is trying to invoke their rights on a whiteboard," Dills said. 

Dever noted the defendant never brought up Marcelle shooting him at that time and said the video refutes the defense argument "no one would listen to him, and no one investigated" his claims. 

Protective order controversy 

Promyss Marcelle, who testified earlier at the trial, previously told WJZ Investigator Mike Hellgren she tried to get help from police in the hours before her son was killed. 

Marcelle said she hid in the bathroom, turned on the shower, and called 911.

She said when officers arrived, they spoke to her and Jones separately. She does not believe all of them took her seriously.

"Police came…laughing like it was a joke—like literally it was a joke," she told Hellgren. "I felt like I was being judged automatically, and it's like—that's my home. It's my kids' home."

Marcelle said police told her, because no crime had been committed and because they saw a piece of mail addressed to Jones on her coffee table, that was enough to show he lived there, and they could not remove him from the apartment. Marcelle said his name was not on the lease.

"Where am I supposed to go?" she asked. "I had no vehicle. …They said I can either leave my home with my kids. I have no family in Maryland. So, I can either leave my home at eight something at night with my kids, or I can get a restraining order, but it still has to be approved from the judge or you have to go to court and it can take a 30-day process," she said.

Feeling she had no other option, Marcelle stayed. 

"We were in my home, where I'm supposed to feel safe. When I didn't feel safe, I called the people who were supposed to help me feel safe, which is the police," she said. 

The trial is expected to continue Friday afternoon. 

Resources, including remote protective orders, are available for victims of domestic violence.     

The National Domestic Violence Hotline is 1-800-799-7233 (SAFE).

People can also text the hotline at 88788 and type "BEGIN" or chat online here.

In Maryland, anyone with questions may also call 211.