Bobby Isidore was the last of three suspects who were in a truck with Leighton Powe Jr. when Powe was fatally shot on Sept. 7, 2013, to be brought in for questioning, Slidell police Sgt. Daniel Seuzeneau testified in court Wednesday as prosecutors prepared to show jurors the videotape of his interrogation.

Isidore, who is on trial on charges of second-degree murder and obstruction of justice, first adamantly denied knowing anything at all, including why he was being questioned. But Seuzeneau told him over and over that police already knew what had happened, that they had a mountain of evidence and that no one else had held back.

Slowly, Isidore began to unspool the events of that day, first denying but then admitting that the plan had been for him and two others to rob Powe of marijuana, not buy it from him. He said he had been asked to go along “in case something happened.’’

But Isidore denied that he held the victim or struggled with him, as Trenton Johnson, the driver of the vehicle, testified Tuesday.

Isidore told police that he didn’t know whom they were meeting at the Dollar General store on Robert Boulevard in Slidell. But when Powe entered the truck, the two former Slidell High School students recognized each other.

“It wasn’t until he got into the truck,” Isidore told the police. “I said, ‘Lee?’ He said, “Bobby?’ Then boom!’’

Isidore said Felix Adams, whom he knew as “Ten,’’ shot Powe before he even realized Adams had pulled out a gun. Isidore said he asked Adams why he had done it, but Adams ignored him.

“I tried to get out at the Dollar General,’’ Isidore told the police. “They kept driving.’’

Isidore did leave eventually — on Javery Road, where Powe’s body was found, face-down in a ditch.

Toward the end of the 90-minute interview, an officer asked Isidore why he had not gone to a neighbor or called police immediately or even later that day to report what had happened. He replied that he had been scared.

But even as police drew more details from Isidore, pressing him to expound on his role in the crime, he denied until the last minutes of the interview that he had grabbed Powe or struggled with him.

Physical evidence of that struggle came out earlier in the day when pathologist Michael DeFatta, of the St. Tammany Parish Coroner’s Office, testified about Powe’s autopsy. He pointed to three marks on Powe’s neck and upper chest that he said were bruises.

He said they likely were caused by the material of a tank top the victim had been wearing as an undershirt. The pattern of the bruising was consistent with the ribbing of the material and likely was caused by his moving back and forth. The left strap of the tank top was torn.

DeFatta also testified that mud and silt in the victim’s nose, mouth and “deep into the lungs’’ indicated that he was still alive when he was put in the ditch on Javery Road, although the cause of death was a gunshot wound to the head.

Defense attorney Jim Burke questioned Seuzeneau about others he had interviewed in the case, asking if Johnson, Adams and others, including the dead man’s girlfriend and best friend, had lied to investigators initially.

Seuzeneau replied that everyone was less than honest at first and tried to minimize their roles.

After Burke’s cross-examination, Assistant District Attorney Julie Knight asked Seuzeneau about Isidore’s claim that he was afraid of Adams. She asked the officer to describe Adams’ demeanor in his interview.

“He was very mild-mannered,’’ Seuzeneau said. “He cried quite a lot.’’

Adams was convicted of second-degree murder and sentenced to life in prison earlier this year. Johnson, who testified in both Adams’ and Isidore’s trials, pleaded guilty to manslaughter.

Isidore’s trial in Judge Alison Penzato’s 22nd Judicial District courtroom will resume Thursday morning.

Follow Sara Pagones on Twitter, @spagonesadvocat.