‘I’m sorry’: She was begging for help to find her sister in Oakland. Then came boyfriend’s alleged confession

OAKLAND — “Please, Amadi.”

The August 2023 text came from the sister of Brenda Diaz, a 30-year-old Bay Area woman who disappeared after leaving her job at an exclusive Marin County fitness club days earlier. The only person who seemed to know something, her boyfriend Amadi Monroe, was being cagey about it, insisting he’d tell Diaz’s sister everything — only if she met face-to-face, according to court records.

Diaz’s sister resisted the meeting, a decision that could have saved her life. By the time Oakland police caught up with Monroe, he was a suspect in two homicides and two nonfatal shootings.

Police allege that he killed Diaz inside her Lexus SUV, then drove her body from Marin County to Oakland, where he shot and killed his cocaine dealer, Jerald Larnell Clark II, court records show. He faces pending murder and gun possession charges. Now, Monroe’s preliminary hearing has offered the public a glimpse into the tragic day in 2023.

Both victims’ loved ones were left with no explanation other than Monroe’s increasingly erratic behavior, fueled by his perception that “somebody” was plotting to murder him.

“You know your sister have (sic) been setting me up to be killed. Don’t act like you don’t know,” he allegedly texted Diaz’s sister.

Testimony describes Clark’s final “I love you” to his wife before he reluctantly left his home to meet Monroe, how an earlier tragedy may have caused Monroe’s mental breakdown, and how Monroe showed up to his mother’s house for one last home-cooked meal before Oakland cops stormed the residence and hauled him off to jail.

The first clue that Monroe was potentially leaving a trail of shooting victims around the Bay Area came when Diaz’s sister received a flurry of hastily-written text messages that would later be read aloud in court. She’d been begging him for information, continuing to press through his evasiveness and insistence on an in-person meeting. Finally, nearly three full days after Diaz’s disappearance, he broke, she testified.

“I’m not gonna lie,” Monroe wrote in one text. He said he was being followed by people who wanted to kill him, and that Diaz was part of the plot. “Dey pullup n g (sic) panic thinking they was gone kill me. I shot bullet hit Brenda. I’ll turn myself in…I’m sorry. I was lost, scared in panic. I’m sorry. I promise wasn’t my fault.”

In the haunting garble of messages, one stood out: “She’s at the pier n (sic) Oakland.” Police followed up and discovered Diaz’s body inside her Lexus SUV, parked on the 900 block of 22nd Avenue, near the Embarcadero waterfront in Oakland. By that time the Lexus had been named as a suspect vehicle in three other Aug. 8, 2023 shootings: one in San Pablo with no victims, another that left a woman bruised from a bullet in Richmond, and the killing of Clark in front of his Oakland home, police testified.

But the story behind the shootings truly begins a year earlier, on Sept. 16, 2022, when a motorcyclist crashed into a fence on Northgate Avenue, catapulting himself down 25 feet to the BART tracks, where he was struck and killed by a train. It was 35-year-old Alvin Monroe Jr., Amadi Monroe’s older brother, and the death gutted the younger Monroe. It was compounded when a West Contra Costa storage unit caught fire, destroying Alvin’s belongings, their mother testified.

Monroe came to believe the fire was no accident, that it was part of a plot targeting him. This led to disturbing and obsessive behavior that was noticed by Diaz, Monroe’s mom, and Clark, whose widow testified she had cautioned him to stay away from the erratic man she knew as “Bang” who would occasionally drop by to buy cocaine.

Even in a police interrogation room after both homicides, Monroe doubled down on the idea that he was being followed, an Oakland detective testified. More than once, he accused Diaz of being part of the plot to kill him, according to both police and members of the Monroe and Diaz family.

On July 20, 2023, just 19 days before Monroe allegedly killed her, Diaz had put up $20,000 to bail him out of jail in a nonfatal shooting case. Judge Thomas Nixon remarked, “I really shouldn’t do that,” before lowering Monroe’s bail from $300,000 to $200,000 at an earlier court hearing, court records show.

Diaz may have sensed danger. The day of her death, she texted Monroe’s mother, “I’m done with your crazy son,” and said that she had lived to regret another fateful decision, according to the testimony.

“I regret putting my name on a bond for your son,” Diaz texted Monroe’s mother. “He’s telling me I’m setting him up.”

Monroe’s mom doubled down.

“You are full of s—,” she replied. “You know Amadi is sick. He got to find himself again. He died when AJ died. If you can’t understand that, that’s on you. You still signed that bail. I love you and Amadi.”

On the witness stand, Monroe’s mother said she remains confident she could have prevented the tragedy that followed. She denied telling Diaz not to call police, even though prosecutors say a text that read “no police” was sent from Monroe’s mother’s phone to Diaz shortly before the homicide.

“I’ve always taught my son do not hurt anybody, no woman, no man, no child, no one,” Monroe’s mother testified. “And I would have stopped it … If he was harming her, doing anything, I’d have stepped into it, right in the middle, and put a stop to it.”

Diaz was allegedly shot and killed at a Target parking lot in Marin County on Aug. 8, 2023, hours before Clark would meet a similar fate. Clark’s widow testified that he told her before walking out the front door he was going to “meet Bang,” then asked, “did you hear me?” Then he walked to the door, hesitated, turned around, and said, “I love you.”

The woman watched him leave, and heard shots ring out moments later. Video from a nearby residence’s surveillance camera captured someone shooting Clark from Diaz’s Lexus, authorities testified. Clark was pronounced dead later that evening, at Highland Hospital.

As Oakland police were discovering Diaz’s body in Oakland on the morning of Aug. 11, 2023, Monroe was exchanging “I love you’s” with his mother. She testified he came to her home and requested his mom make him chicken. She prepared the meal as she’d done many times before, then went outside to drink a beer while he ate, she testified.

“The next thing, the police was grabbing me to get me away. I didn’t know what was going on,” she testified.

Monroe has been in jail ever since. His next court date has been set for June 12, but the trial hasn’t yet been scheduled.