Carter offered one alibi, then another. Perez let Carter talk, then told him how witnesses contradicted his account. Each time Carter faced a contradiction, he retreated a little, changing his story.
Eventually, he admitted that he had picked up a companion that morning -- and that they had driven to the mouth of the alley, stopped and opened the trunk.
It was a breakthrough. Carter had put himself at the scene.
Perez told Carter that he had a choice: Give up the shooter or be charged as the chief murder suspect.
"It's the homies or your kids," Perez said.
Carter stuffed his hands in his pockets, stared at the table, crying silently. "What chance of me getting out of here?" Carter finally asked.
Perez sighed. "Depends on how much you help."
Carter furrowed his brow, looked down.
Arenas chimed in: "Your cousin is caught up in this too," he said.
Carter looked at the ceiling and sucked in his lips.
Regarding his own actions, he said, "Ain't nothing I can do about it. I can accept it. But my little cousin ... he had nothing to do with it."
Arenas and Perez barreled out of the interview room about 4:30 p.m., and the squad crowded around, peppering them with questions.
They hadn't gotten everything they wanted, but Carter had confirmed key elements of witness accounts.
Arenas, mostly frustrated since joining the squad, now found himself in the spotlight. He pointed to Perez. "It was Benny!" he said.
Zambos leaned against the wall as Arenas recounted the interview. "Beautiful," Zambos said.
The detectives had more work to do. They checked back with witnesses and gleaned new details.
By 5 p.m., they had a full account of the killing, plus a description of the shooter and two of his nicknames.
Pantoja bent over his computer, searching the state database of gang members. He sang softly as he tapped the keys.
Pantoja clicked on a photo. The names matched, but this gangster was nearly 30.
That's not him, Zambos said: We're looking for a teenager.
Pantoja bent over the keys again.
A second later, he sprang up. This time, everything matched -- gang monikers, physical description, name, address.
"It's him!" Pantoja said. He peered more closely at the screen. "A baby. We are going to arrest a baby."
"How old is he?" Zambos asked.
The suspected shooter was the same boy that Det. Nickerson had promised to take to a ballgame -- the boy whose mother's phone message Nickerson had not returned. He was arrested in the stairwell of an apartment building not far from the Southeast station.
About 8 p.m., he was seated in a swivel chair at the end of the squad room, his thin neck protruding from an enormous black hooded sweatshirt.
He had wide, bright brown eyes and a thin scar across the bridge of his nose.
Zambos glanced at him as he walked by. The boy was slumped far back in the swivel chair, expressionless.
"Sit up," Zambos said.
The boy straightened.
"How come you told me you were in Carson when your mom told me you were out riding your bike?" Zambos asked. The boy's eyes widened.
"No, sir!" he protested. "I forgot." He began to argue. Zambos cut him short.
"Good luck with yourself," Zambos said, and walked back to his desk.
The boy swiveled back and forth, playing with the strings of his sweatshirt hood as he was booked on suspicion of murder.
Detectives pieced together this account of the slaying: Carter picked up the boy just before the shooting. As they drove by Tam's, Wesley was at the restaurant window, ordering breakfast. One of the car's occupants pointed to Wesley and asked if he was from a rival gang.
"I think so," someone answered. Carter then drove the boy to the alley. The youth ran to Wesley's Suburban.
The teenage girl waiting in the Crown Victoria turned up the stereo, masking the sound of gunfire.
Police believe the boy shot Wesley in a gang initiation rite, mistaking the Pep Boys salesman for a rival gang member.
Wesley's ex-girlfriend was not involved, Zambos said. He never learned why she had lied about having a cellphone.
Nor did police find the murder weapon.
Zambos was able to close the case and keep the murder book the way he liked it: neat, free of excess detail.
Murder charges were filed against Carter, accused of driving the car, and against the boy, accused of fatally shooting Wesley. Both are awaiting trial.
The homicide squad, meanwhile, carried out a heist on Arenas' behalf. They stole a computer from patrol, hid it in a closet until the clamor died down, then installed it on his desk.
It was overcast, dark and cold when Zambos and Pantoja headed out of the office. The weather was shifting into a pattern of heavy rains. Zambos played Christmas carols on the radio and sang along. Pantoja drove fast.
Both were cracking silly jokes -- Pantoja chuckling as Zambos laughed himself weak. Zambos had been looking forward to this moment. He loved bringing news of arrests to victims' families.
As they walked up to the Wesleys' door, Zambos jiggled his keys.
They were back in the room with the snow-white rug.