Four suspects have now been arrested in the killing of two police officers in Hattiesburg, Mississippi. Getty Images

More details have come to light as police in Hattiesburg, Mississippi, continue to investigate the Saturday night shooting that left two police officers dead. Cornelius Clark, 28, has been arrested and charged with obstruction of justice, reports Mississippi's WDAM.

The arrest came just hours after Hattiesburg mayor Johnny Dupree revealed that suspect Joanie Calloway, 22, had been the driver of the car that officer Benjamin J. Deen pulled over. Clark was allegedly also a passenger in the vehicle at the time of the shooting.

Two brothers have also been charged in connection with the killings. Marvin Banks, 29, has been charged with two counts of capital murder, among other charges. Curtis Banks, 28, was charged with accessory after the fact to capital murder.

Calloway was charged with two counts of capital murder.

The killings of the officers -- Deen, 34, and Liquori Tate, 25 -- have shaken the southern Mississippi town, which hasn't seen a member of law enforcement killed since 1984. Gov. Phil Bryant expressed his condolences in a statement Sunday morning.

“Deborah and I join all Mississippians this morning in mourning the death of our two police officers in Hattiesburg: This should remind us to thank all law enforcement for their unwavering service to protect and serve," he said in the statement. "May God keep them all in the hollow of his hand.”

Officer Deen was a K-9 officer who was recognized as officer of the year in 2012. Tate was in his first year on the force.

Police said that Deen pulled a vehicle over around 8 p.m. Saturday night and called for backup. Soon afterward, Deen and Tate were discovered mortally wounded by area residents. They were pronounced dead shortly after at a local hospital.

The Banks brothers were arrested in separate locations early Sunday morning. All four suspects are expected to make their first public appearances Sunday afternoon.