William Stallworth kept his eyes fixed on the floor.

His hands were cuffed and a chain was wrapped tightly around his waist.

He's been behind bars since early Friday morning.

On Monday, the 25-year-old Tulare man was charged with murder and assault on a child causing death. He also faces a special allegation that he caused his 2-year-old son — William Stallworth Jr. — great bodily injury.

Joyce Graham, Stallworth's mother, was at Tulare County Pretrial Facility on Monday to support her son. She wanted him to know she would always be there for him.

"I disagree with the charge (homicide)," she said. "He's not a murderer."

Police believe otherwise.

They have pointed toward Stallworth as the person responsible for the toddler's death.

Stallworth called 911 just before 6 p.m. on Thursday to report that his son had been shot in the head.

The shooting happened inside a vehicle parked at a home in the 2400 block of West Sweet Court, near Woodland Park. Stallworth doesn't live at the home, but the boy's mother does, according to police.

She wasn't home at the time.

More:Here's what we know about the man accused of killing 2-year-old son

More:UPDATE: Gun missing in Visalia toddler's death, another suspect remains at large

The circumstances around the toddler's death remain unclear.

The toddler was playing in Stallworth’s vehicle alone when he grabbed a loaded gun in the center console and suffered a single gunshot to the head, according to investigative reports submitted by detectives to the District Attorney's Office.

"The circumstances surrounding this incident are still under investigation," said District Attorney Tim Ward. "Anyone with further information should contact the Visalia Police Department or the office of the District Attorney."

Detectives believe the gun went off and then Stallworth handed the gun to a man, who fled the area. His role in the death is unclear, but he's believed to have the gun used to kill the toddler.

That person is wanted by detectives for questioning, Police Chief Jason Salazar said.

A description of the man wasn't given by police.

Following the shooting, Stallworth was detained by detectives and later arrested on suspicion of homicide and child endangerment.

Graham said she knows her son didn't intentionally kill her grandson.

She said her son and grandson were inseparable. Graham described William Stallworth Jr. as a "joy."

"It was a freak accident," she said.

A preliminary hearing is set for Sept. 19.

Sheyanne Romero covers Tulare County public safety, local government and business for the Visalia Times-Delta and Tulare Advance-Register newspapers. Follow her on Twitter @sheyanne_VTD. Get alerts and keep up on all things Tulare County for as little as $1 a month. Subscribe today.