A D.C. police office has been found guilty Thursday of first-degree murder in the deaths of his former mistress and their child.

A Prince George's County jury deliberated less than two hours before finding Richmond Phillips guilty of two counts of first-degree murder in the killing of Wynetta Wright, 20, and 11-month-old Jaylin Wright.

Phillips faces two life sentences in prison without the possibility of parole plus 20 years in the killing at his sentence scheduled for March 22.

Prince George's County State's Attorney Angela Alsobrooks said Phillips, 40, fatally shot Wright and then left Jaylin "to cook" in a car outside a Hillcrest Heights community center because he did not want to pay child support. He was married.

The killings took place in May 2011, the night before the two were scheduled to go to court for a hearing in a paternity case. Phillips was supposed to submit a DNA sample that would prove he was the father of Jaylin, prosecutors said.

Phillips, of Hillcrest Heights, and Wynetta met at the Oxon Run Stream Valley Park, prosecutors said.

He used his personal weapon to shoot Wynetta in the head, then dragged her body to a nearby wooded area.

The officer then drove Wright's car with their daughter inside to an apartment complex a short distance away.

He left Jaylin strapped inside a baby seat and walked away, allowing her to "essentially, to cook in that car, hoping and praying that she would never be found," Alsobrooks said during opening arguments.

Their bodies was found several days later. Police say the girl may have died as a result of exposure to the heat.

Temperatures likely reached 125 degrees inside the vehicle.

During the nearly four-day trial, prosecutors showed surveillance video and phone records that they said showed Phillips was in the park on the night of the shooting. And the defendant's DNA was recovered from the victim's car.

Phillips worked in undercover narcotics at the District police department. He has been suspended without pay, a department spokeswoman said.

Staff writer Naomi Jagoda contributed to this report.