Quanell X explained, "He was thinking about running, fleeing. I talked to the brother and explained that's the worst thing he could do."
Investigators say Brewer was shot after getting into an argument with Sonier, accused of being a pimp, over money following sex with a prostitute.
Also charged with capital murder is the alleged prostitute, Judy Lucille Hambrick, who is currently jailed.
On Tuesday, police questioned Sonier, 31, Hambrick, 40, and another woman. Sonier and the unnamed woman were released pending further investigation. Hambrick remained in custody and was charged with theft of a firearm. Police say she admitted to stealing Brewer's weapon.
According to a probable cause affidavit released Friday, Hambrick performed a sex act on Brewer in his car early Tuesday morning. Afterward, police say Sonier argued with Brewer and shot him.
Houston police would not talk publicly about the case; neither would prosecutors. But HPD did send out a press release around midday Friday asking for the public's assistance to find Sonier after a noon time surrender did not happen as planned.