A second suspect has been arrested in the killing of Joshua Brown

A second suspect has been arrested in the killing of Joshua Brown, a key witness in the murder trial of a former Dallas police officer convicted of shooting their neighbor in his own apartment.

Brown testified against former officer Amber Guyger who fatally shot their neighbor, Botham Jean. Guyger said she killed the 26-year-old accountant after she mistakenly walked into his apartment, one floor above her unit, and mistook him for a burglar.

Ten days after testifying for the prosecution in the high-profile trial, Brown was shot dead Friday during a drug deal gone wrong, Assistant Chief Avery Moore said.

He was killed after an argument with one of three Louisiana men who had met him in Dallas for a drug purchase, Moore told reporters.

Police identified the men as Thaddeous Green, Jacquerious Mitchell and Michael Diaz Mitchell.

Up until Tuesday, only Jacquerious Mitchell, who was hospitalized, was in custody. US Marshals arrested Michael Mitchell on Tuesday evening in Marksville, Louisiana, police said. CNN has reached out to the Avoyelles Parish Sheriff’s Office for additional details.

The alleged drug deal

A conversation between Brown and Green escalated into a physical altercation during the alleged drug deal. Brown allegedly shot and wounded Jacquerious Mitchell, 20, police said.

Green then shot Brown twice, then took a backpack from him as well as the gun used to wound Mitchell, police said.

After receiving tips, police obtained a search warrant and recovered 12 pounds of marijuana, 143 grams of THC cartridges and $4,000 in cash from Brown’s apartment.

“As you know, there’s been speculation and rumors that have been shared by community leaders claiming that Mr. Brown’s death was related to the Amber Guyger trial, and somehow the Dallas Police Department was responsible,” Moore said.

“I assure you that is simply not true. And I encourage those leaders to be mindful of their actions moving forward because their words have jeopardized the integrity of the city of Dallas as well as the Dallas Police Department.”

Attorney S. Lee Merritt represents Brown’s family and has called for Dallas police to recuse themselves from the investigation into his shooting.

“This family and their representatives have consciously avoided speculating about law enforcement involvement in this tragedy. However, due to the proximity of this murder with the trial of Amber Guyger — rumors abound, ” Merritt said in the statement posted on his Instagram page.

“It is important for everyone involve(d) that this case not only be solved but the conclusions arrived to by investigators be seen as authentic and reliable.”

Jean’s shooting

Guyger shot Jean on September 6, 2018.

Brown said he returned home that night from watching a football game at a sports bar around the same time Guyger walked into Jean’s apartment. Brown was down the hall when he heard voices of two people who sounded like they were meeting by “surprise,” he testified.

He testified he heard shooting right after and didn’t hear any police commands like “Show me your hands,” before the gunshots rang out. But he said it was difficult to make out the words between Guyger and Jean.

Guyger was convicted of murder and sentenced to 10 years in prison last week.