A Philadelphia jury on Friday found a 22-year-old South Philadelphia man guilty of first-degree murder for shooting his girlfriend after she said she was pregnant with his child.

The Common Pleas Court jury of six men and six women returned its verdict against Aaron Fitzpatrick in its fourth day of deliberations, finding him guilty of shooting of Tiffany Gillespie, 24, in 2012.

The jury, which on Thursday indicated it was deadlocked on all but two charges, also found Fitzpatrick guilty of third-degree murder in the death of the 5-month-old fetus Gillespie was carrying, and two firearms counts.

Fitzpatrick frowned and shook his head side to side as he heard the verdict. He was silent when Judge Steven R. Geroff asked him whether he had anything to say before Geroff imposed two concurrent life prison terms without possibility of parole. The sentence is mandatory.

"I don't understand what was going through your mind," Geroff told Fitzpatrick. "I don't know what possessed you to shoot this lady in the back of the head, but that's all on you."

Defense attorney Stephen P. Patrizio said he did not know whether Fitzpatrick would appeal.

Gillespie's body was discovered by her mother about 2:20 a.m. in the basement of their home in the 2300 block of South Mildred Street.

At the time, police said Fitzpatrick and Gillespie had been arguing after she told him she was pregnant about six months with either twins or a girl. Gillespie already had a son, 8, and a preschool daughter.

Neighbors said the family had financial problems and that Fitzpatrick and Gillespie had public altercations that sometimes required police intervention.

None of Gillespie's relatives were in court for the verdict and Assistant District Attorney Joanne Pescatore said they did not wish to make victim-impact statements.

"This was a very upsetting case: just the circumstances of a pregnant woman who was also using drugs," Pescatore said.

Pescatore said postmortem DNA testing showed Fitzpatrick was not the father of Gillespie's unborn child.

Fitzpatrick, who did not testify in his defense, gave two statements to police homicide detectives in which he admitted shooting Gillespie, describing the act as one of frustration in a long, increasingly dysfunctional relationship.

Fitzpatrick told detectives the relationship began with him providing Gillespie with crack cocaine for sex. After she told him she was pregnant, Fitzpatrick's statement said he was not ready to become a father and "just gave her drugs to shut her up."

Fitzpatrick's statement said Gillespie threatened his life and continuing nagging him for crack cocaine.

On Feb. 16, 2012, according to a statement Fitzpatrick gave detectives, Gillespie called about 1 a.m. and told him to come to the Mildred Street house so they could argue.

"I didn't want to argue with her, so I shot her in the head and left," Fitzpatrick's statement reads.

At trial, Patrizio challenged the circumstances under which Fitzpatrick made that statement and also focused on the victim's crack-cocaine use.

Pescatore argued that forensic testing found Fitzpatrick's DNA on the .38-caliber revolver proven to be the murder weapon and that Gillespie's blood was found on his clothing.

Both gun and clothing were found hidden in the South Philadelphia home of Fitzpatrick's aunt; she testified that he came to her house on Feb. 16, 2012, to change clothes and wash up.