Officers heard several gunshots, and when they went to the room, found both Smith — a married father — and Powell dead of multiple gunshot wounds, police said.
Police in Jackson, the capital of Mississippi, were clearly shaken by the killing of one of their own inside a high-security building where officers and residents alike expect to be safe. But they did not release any details about what they believed happened. They said the case has been turned over to the Mississippi Bureau of Investigation, which is standard procedure.
"The entire city of Jackson and the Jackson Police Department family are all hurting," said Jackson city spokesman Chris Mims. "We are asking for the public's patience while we find out why this tragic incident happened and how it happened."
The suspect was being questioned on the third floor of the police headquarters building when the shooting happened, Police Chief Rebecca Coleman said.
Police said in a news release that Powell was in the process of being arrested in the killing Monday of 20-year-old Christopher Alexander. News outlets reported that Alexander's body was found Monday near a Jackson street and he had been stabbed in the neck.
The police headquarters was on lockdown Thursday night, Mims said.
Jackson City Councilman Chokwe Lumumba was in police headquarters with the mayor later and said Smith was shot by the suspect. He did not know how the suspect ended up dead.
"I understand there may have been more than one police officer in the room," Lumumba said.
The headquarters was blocked off and surrounded by crime tape. Law enforcement and Jackson city officials rushed to the scene.
At least 30 Jackson Police and Hinds County Sheriff's office vehicles were haphazardly parked across multiple, major downtown Jackson streets Thursday evening. Officers wiped their eyes, and Assistant Chief Lee Vance could be seen comforting Coleman at one point, putting his arm around her shoulder outside the building.
Mims described the 40-year-old Smith, who was assigned to the Robbery-Homicide Division, as "a decorated detective and well-respected law-enforcement person throughout the state of Mississippi."
A 2008 photo on the department's website shows Smith, in a shirt and tie, accepting a certificate of commendation, with Coleman and Vance on either side of him.
Lumumba, who is a lawyer, said he first met Smith in the late 1990s. The then-officer had testified on some of Lumumba's cases.
"I had great respect for his work and his integrity," Lumumba said. He added that Smith's stepson had played basketball on an Amateur Athletic Union team that Lumumba worked with.
"Eric helped take young men all over the country," the councilman said. "He's a real man in every sense of the word."
Mayor Harvey Johnson, Jr. also addressed the officer's death.
"Detective Smith was an excellent officer in all respects," the mayor said. "I want everyone to keep the Smith family in their prayers and in their thoughts."