Latara Walker sat in the witness chair in a Gretna courtroom Wednesday afternoon, carefully avoiding eye contact with her cousin, Antoine Johnson, as she described the night she arrived at a Terrytown apartment complex two years ago to find her best friend, Aaron Roby, had been shot 13 times and killed.

Walker, a witness for the prosecution, would glance at Johnson only long enough to identify him to the jury on the opening day of testimony in Johnson’s second-degree murder trial in 24th Judicial District Court.

Johnson, 27, is accused of gunning down Roby in the rear courtyard of the Holmes Boulevard apartment complex on April 21, 2013, two weeks after the men had an argument.

Roby was found unresponsive by police just after 10 p.m., his head, body and limbs riddled with 21 entrance and exit wounds.

“He was a real good friend,” Walker said, tearing up as she described Roby as willing to help friends any time he could. “He was like my best friend. He was always there for me.”

Walker testified that she came to the complex after getting a call from her mother, who also lives there. She did not know what had happened when she arrived, but after stopping by Roby’s apartment and finding he wasn’t home, she went around to see if he had taken out the garbage and found the police, who asked her if she could identify the body.

Walker testified she had recently talked to Johnson’s girlfriend, Sabrina Johnson, about the argument the two men had had, and she told the police that night that she was certain that Antoine Johnson was the killer.

“He didn’t have any enemies,” she recalled telling the police about Roby. “My cousin did that, Antoine Johnson.”

Under cross-examination by defense attorney Joseph Perez, however, Walker conceded she didn’t witness anything firsthand. He asked if she had “any other opinions” about the case.

According to court documents, Sabrina Johnson told investigators that she and Antoine Johson had gotten into an argument one night two weeks before, and Roby, who had recently gotten Sabrina Johnson a job working for him at the Naval Air Station-Joint Reserve Base in Belle Chasse, came to the door to ask them to lower their voices.

They did, but then the argument got loud again and Roby returned. This time, the two men argued and had to be separated by Walker’s mother, who is Antoine Johnson’s aunt.

Sabrina Johnson told detectives that on the day of the killing, she and Antoine were driving to a restaurant in Kenner and began arguing again. She chided him for being threatening to women and children while in the argument with Roby, he “folded like a bitch.”

She told investigators they didn’t go to dinner but instead drove to the Metairie apartment of his cousin, Coy Moore, where Antoine Johnson went inside for 10 minutes, then left with Moore to meet with another man for 10 minutes before returning to the car.

Sabrina Johson told investigators that Antoine Johnson took her back to her apartment and that she thought he had left, but she looked outside and saw his white Infiniti was still there.

She called him at 9:43 p.m., according to phone records, and he said he was talking to her neighbor, whom she assumed was Roby.

A few minutes later, 13 shots rang out and Sabrina Johnson called Antoine Johnson again, at 10 p.m. She said he told her not to call him anymore.

The police report said Sabrina Johnson was crying after they found her and said, “This is all my fault.”

Investigators said in court documents that Antoine Johnson’s phone was shut off about 20 minutes later, and that the Infiniti was found several days later in front of Moore’s apartment. Antoine Johnson was picked up by U.S. marshals in San Antonio the following month.

Johnson, 27, is facing possible life in prison without benefit of parole, probation or suspended sentence.

The trial continues Thursday.

Follow Chad Calder on Twitter, @Chad_Calder.