A 3-month-old Sharon boy, who police say suffered a serious brain injury when his father shook him, has died and police plan to charge the man with the baby’s death.

“Unfortunately, the baby passed away last night,” Sharon Police Capt. Michael Menster said Saturday.

Menster said he plans to charge Thomas M. Mortimer, 24, of 247 Jefferson Ave., with criminal homicide Monday. Dillon Mortimer died at 10:25 p.m. in Children’s Hospital of Pittsburgh, where he had been in the intensive care unit since the June 3 incident.

“The baby died as a result of injuries sustained in that incident,” Menster said.

The baby’s cause of death was ruled homicide Saturday morning by the Allegheny County Coroner’s office, which performed an autopsy. The office still has several tests to run before it can determine Dillon’s exact manner of death, Menster said.

Police consulted with Mercer County District Attorney James P. Epstein on charging Mortimer with homicide. If convicted, Mortimer could face the death penalty or life in prison, Epstein said.

“We have sufficient evidence to prove he was responsible for the baby’s death,” Epstein said.

Police were called at 7:14 p.m. June 3 to Mortimer’s home on a report of an unresponsive child. Dillon was taken to the hospital of Sharon Regional Health System and then flown to Children’s Hospital.

Mortimer was also watching his 18-month-old daughter at the time and he told police he tripped and fell while carrying Dillon, whose head hit the floor.

Mercer County Children and Youth Services told Sharon police June 4 that Dillon’s injuries weren’t indicative of a fall. A doctor told police Dillon had no external injuries but suffered brain bleeding and internal injuries that were consistent with having been shaken.

Police questioned Mortimer June 5 and said he admitted he shook Dillon once or twice because he was frustrated over the baby’s crying. Menster said Mortimer shook Dillon until he stopped crying, then panicked and called 911.

Police arrested Mortimer June 6 in the 500 block of North Oakland Avenue and charged him with aggravated assault. Allegheny County Children and Youth Services assisted in the investigation.

Mortimer is in Mercer County Jail on $100,000 bond for the assault charge. Epstein said bail cannot be set for homicide because of the seriousness of the charge.