Attorney S. Lee Merritt represents Brown's family and has called for Dallas police to recuse themselves from the investigation into his shooting.
Green then shot Brown twice, then took a backpack from him as well as the gun used to wound Mitchell, police said.
Authorities also said at the news conference that Jacquerious Mitchell, 20, one of three suspects sought on capital murder charges in Brown's killing, is in custody at a hospital.
Green and the Mitchells allegedly drove from Alexandria, Louisiana, four and a half hours east of Dallas, to meet Brown for a previously arranged drug deal for marijuana.
The Reverend Michael Waters, pastor of Joy Tabernacle African Methodist Episcopal Church in Dallas, who has been pushing for police reform in the city, said the speculation around Brown's death is driven by "generations" of mistrust for the police that's grown out of wrongful convictions and abuse.
Joshua Brown was a neighbor of shooting victim Botham Jean at the South Side Flats apartments.
Green and Mitchell are still on the run and police consider both to be "armed and unsafe".
Jacquerious was in custody at a local hospital, and authorities said they would issue a capital murder warrant for him.
In a search of his apartment, officers found 12 pounds of marijuana, 149 grams of THC cartridges and more than $4,000 in cash, police said. But he's asking the department to turn the investigation of Brown's death over to another agency.
The third suspect, Thaddeous Green, 22, remained at large.
He stated during the press conference, "The rumors shared by community leaders that Mr".
Following Brown's killing, rumors had circulated that Dallas police may have been involved in the homicide because Brown testified against Guyger, who is a former Dallas police officer. Shaun King announced a reward of $100,000 for information leading to the arrest of those who killed Brown.
© Tom Fox/The Dallas Morning News via AP Botham Jean's neighbor Joshua Brown answers questions from Assistant District Attorney LaQuita Long at Amber Guyger's trial on September 24, 2019. But what he described as a "physical altercation" begins between Green and Brown.
Brown lived on the same floor as Jean.
Moore chastised those who implied that police were somehow linked to Brown's death.
Brown testified in recent weeks that he heard two people who sounded like they were meeting by "surprise", according to CNN, then gunshots followed.
Brown was found in a parking lot outside an apartment building with multiple gunshot wounds two days after Guyger was convicted of murder.
"These suspects are to be considered risky, because they are armed", Moore said.