17-year-old Tynia Johnson faces a capital murder charge. (Dallas Police Department)

A 17-year-old girl faces a capital murder charge in the death of a 3-month-old boy, according to NBC.

Tynia Johnson was babysitting Ashton Smith on Sunday, Feb. 16. Around 12 p.m., Johnson called his mother and great uncle and said the baby was ill.

His great uncle, James Pedyfoot, picked Ashton Smith from Johnson in the 11000 block of Walnut Hill Lane. Pedyfoot then picked up his mother, Aspen Smith, from work. Together they took Ashton to Dallas Regional Medical Center in Mesquite.  Ashton was then transferred to Children’s Medical Center Dallas due to the severity of his injuries.

Pedyfoot told authorities Ashton was breathing irregularly and his arms were stiff when he picked him up from Johnson.

Doctors later said the baby most likely had a traumatic brain injury and found a skull fracture, consistent with blunt force trauma.

Smith told Dallas News that Johnson said Ashton had been in a car seat all day, except to have his diaper changed and to eat.

“I don’t believe that’s the truth, because I’ve never seen anyone get a skull fracture from just sitting in a car seat,” Smith told Dallas News.

Ashton Smith was pronounced dead at 4:24 p.m. on Feb. 19. Johnson remained at Dallas County Jail Monday with $150,000 bond.