Thomas Gilbert Jr. had a promising life ahead of him, the kind that a privileged upbringing would all but guarantee.

Born to a financier father, Thomas Gilbert Sr., and doting mother, Shelley Gilbert, he attended Manhattan’s tony Buckley School from kindergarten to ninth grade, and then Deerfield Academy, an elite Massachusetts boarding school. There, he took advanced placement calculus and biology, and became conversant in Chinese. The hedge funder’s son played football, basketball and baseball. After graduating high school, Gilbert Jr. went to Princeton, where he was a legacy student—the father and son were known as Tom and Tommy, respectively.

It seemed that Tommy wouldn’t become a rich city kid who partied his life away on mommy and daddy’s dime. Little did anyone know that Tommy would turn into a parentally subsidized surfer—let alone that he would spiral into obsession and paranoia. And they certainly couldn’t predict that at age 30, Tommy would stand accused of killing his father in an alleged dispute over his weekly allowance.

Manhattan prosecutors began laying out their case against Tommy this week, presenting a comprehensive chronology and new, grisly details about this Jan. 4, 2015 slaying. Tommy did little with his life after graduating Princeton, spending “most of his time surfing, playing tennis, working out and partying,” prosecutor Craig Ortner told jurors in his opening statement on Tuesday. Tommy’s parents covered the rent for his apartment in Manhattan’s desirable Chelsea neighborhood. They took care of Tommy’s car payments, auto insurance, and “even paid his parking tickets for him.” All the while, they gave Tommy a whopping $1,000 per week allowance.

But Tommy was becoming more and more antisocial and was “involved in a series of incidents.” (Ortner didn’t detail these incidents, Tommy was reportedly suspected of setting fire to an historic house in Sagaponack, Long Island.) “They came to realize they had to do something to get him under control,” Ortner said. “One form of leverage, one tool of discipline they still had over him: money.” While they kept paying Tommy’s living expenses, they started cutting his allowance.

That January day, when Tommy arrived at his parents’ apartment in the comfortable Turtle Bay neighborhood, his allowance was down to $300 per week. Shelley heard a knock at the door. She opened it and was ”surprised and happy to see her son standing there.” The Gilberts weren’t expecting Tommy, and he hadn’t called ahead of time. Tommy told her he wanted “to talk business” with his dad. While there was the “pretext” of a professional conversation—Tommy occasionally did work at his dad’s nascent hedge fund—“something was a little off,” Ortner said.

Tommy told his mom that he wanted a sandwich. She offered to make him one at home, but Tommy said he wanted a Coke as well. Tommy knew his mom didn’t keep Coke around, so she would have to go out—leaving him alone with his dad. Shelley left the apartment, hoping Tommy and her husband would make amends. Shelley hadn’t made it far from the building when she started to worry: Would they argue? Shelley “literally walked around in circles, trapped in her indecision what to do next,” and came back after just five minutes. The hall outside their apartment was eerily quiet. The door was locked but not with a deadbolt, Ortner said.

Shelley stepped into the living room. No sign of her husband or Tommy. Shelley called out for the men. Nothing. Shelley then walked into the bedroom. Tom was “lying dead on the floor, blood and pieces of brain matter oozing” out around his head. There was a gun on Tom’s chest, with his “lifeless left hand on the handle... as if someone wanted it to appear it was suicide.” But Tom, who had just turned 70, didn’t keep a gun in the house and “was the last person in the world” who would commit suicide, Ortner said.

“My husband is, I think, dead,” a distraught Shelley told a 911 operator.

Shelley was then put on the line with another operator, who told her to perform chest compressions. Left hand on the center of his chest, second hand on top of the first, he said.

“I’m pressing down...like hospital shows,” Shelley said.

“I think he’s been dead,” Shelley remarked as he led her through CPR. “He’s been shot.”

“He’s been shot?”

“Yes.”

Several moments later, the first operator returned to the line.

“You said your husband was shot? “

“Yes.”

“By whom?”

“My son— who is nuts. But I didn’t know he was this nuts,” Shelley said. “I had no idea he was this nuts.”

Tommy holed up in his apartment after the killing. After hours of refusal, he was arrested late that evening. Police discovered a credit card skimmer and blank credit cards in the apartment. Analysis of his computers later revealed Google searches on making fake cheques—and visits to websites such as “hireakiller.com” and “findahitman.com”

In the years since Tommy’s arrest, his trial had been delayed due to questions about whether he was mentally fit to stand trial. The rakish Tommy sported a white button down shirt and his thinning, long hair was pulled back. He mostly kept his head down during the proceedings, sometimes rocking slightly in his chair.

Prosecutors contend that while Tommy may have had issues, none of the doctors who had treated him over the years had ever recommended anything beside therapy and medication—and that he was not “legally insane.” Tommy was cognizant enough to worry about the press waiting for him outside the precinct after his arrest, asking whether there was another exit they could use, to avoid having his photo taken. He even chatted with detectives about his workout routine and diet, Ortner said.

When prosecutors called Shelley to testify this week, she often framed her answers about Tommy’s behavior in the context of “sickness.”

“ When he murdered his father, the defendant was fully aware of what he was doing and he certainly knew it was wrong ” — Manhattan Prosecutor Craig Ortner

Tommy, who at age 10 gave his father a “Best Dad in the World” figurine, worried about things getting “contaminated” in late high school. Princeton wound up being so “contaminated” that Tommy wanted to transfer. Tommy left college after a semester and wound up in South Carolina, where he surfed, Shelley said.

The prosecution asked at one point whether Tommy had left Princeton because of drugs, including marijuana, cocaine, and hallucinogenic mushrooms.

“He was self-medicating,” his mother said.

At several points when Shelley recalled Tommy’s school days, including a recollection of him spending quality time with Tom, he said “objection!” from his seat at the defense table.

During a break, Justice Melissa Jackson warned that he would be booted from court if he kept having outbursts. Tommy told Jackson that he wanted to say something. He rattled off legal terms in a seeming rant about “prosecutorial misconduct” and “bias during cross-examination.” He asked for a new lawyer, which Jackson denied. Tommy’s attorney, Arnold Levine, asked Jackson for a mental competency exam, saying he was actively “sabotaging” his defense. Jackson, who previously determined Tommy was competent to stand trial, denied Levine’s request.

Shelley also testified that she and Tom repeatedly tried to get him into a hospital but were left with few options because Tommy was an adult. While she and her husband considered forced hospitalization, they figured he would get out after a few weeks anyway. “We thought we’d had an extremely angry mentally ill child on our hands, rather than just a mentally ill child on our hands…”she said.

When asked about him being able to graduate from Princeton, albeit later than expected, Shelley surmised “different parts” of the brain controlled his disease and intellectual ability.

“His wasn’t a discipline problem. It wasn’t a rebellion problem. It was a disease,” she later said of Tommy’s do-nothing life in New York City. They were supporting him to “keep his life as normal as possible,” hoping it would be “therapeutic,” she said.

When the volley of direct and cross testimony concluded Wednesday afternoon, Shelley left the courtroom, met by a throng of reporters and photographers. She was sporting a black skirt and cream-color sweater.

“It’s very difficult,” she said, when asked about testifying against her son.

Shelley, who had been a constant courtroom presence throughout the case, said she was leaving for the day.

“I’m exhausted. I’m going home,”she told reporters. “This is just police procedure this afternoon. I don’t need to relive it.”