A Princeton graduate who was on Monday charged with murdering his multimillionaire father and attempting to stage the death as a suicide was also the prime suspect in an arson attack that burned down a rival's Hamptons mansion, it has been revealed.

Tommy Gilbert Jr, 30, was arrested in September for violating a restraining order taken out by Peter N. Smith, days after Mr Smith's father's home went up in flames.

Princeton graduate Gilbert Jr appeared in court charged with shooting dead his father, Thomas Gilbert Sr, at the family's luxury Manhattan apartment in a fight over his allowance being cut.

The Ivy Leaguer was a mainstay at New York society black-tie events in recent years but one ex-girlfriend revealed details of his dark side on Monday.

Manhattan socialite Anna Rothschild, 49, whom he dated last year, said Tommy was a loner with few friends who deeply resented his father and was obsessed with how he would 'never be good enough' for his dad.

Reports were also emerging today that Gilbert Jr suffered from mental illness and had been off his medication prior to the shooting.

Gilbert Jr was charged with murder and criminal possession of a weapon along with 21 counts of criminal possession of forgery devices after skimming device and 21 blank credit cards were found at the Chelsea apartment his father paid for.

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Tommy Gilbert Jr, 30, appeared in court late Monday to answer charges of murder and criminal possession of a weapon following the shooting death of his father on Sunday

Thomas Gilbert Jr, 30, seen here being transported into Manhattan Central booking by police for the murder of his father Thomas Gilbert Sr. He wore sweatpants and no socks

Gilbert Jr.'s ex-girlfriend Anna Rothschild, 49, says he was a loner whose phone only rang when his mother called. The two are pictured together at a charity gala at the Jane Hotel in last January

Thomas Gilbert, founder of Wainscott Capital Partners, (pictured right) was allegedly shot in the head by his son Tommy Gilbert Jr (left) after an argument

On September 15 last year, a blaze destroyed a beautiful Hamptons home owned by retired investment banker Peter Smith Sr and his family

The 30-year-old was being held in custody until his next court hearing on Friday.

Cops say Gilbert Jr visited the Midtown Manhattan home, asked his mother to go and buy a sandwich, shot his father dead and left the gun in the victim's left hand to make it look like a suicide before fleeing.

Police later found the box the gun came in and ammunition that matched the murder weapon at Gilbert Jr's home, investigators said.

As the Daily Mail Online first reported Monday night, that Gilbert Jr. is suspected in the September 15 blaze that demolished a historic 19th century mansion in Sagaponack in the Hamptons. The New York Post and New York Daily News both report he is the prime suspect

No one has been arrested or charged, however, a gas can and gasoline-soaked cloth was found in a nearby cemetery and Southampton police are investigating the case as an arson.

Gilbert Jr.'s ex girlfriend - twice-divorced Upper East Side socialite Anna Rothschild - told the Post that her former flame was a loner who had few friends and never got phone calls.

The only person who ever called him was his mother, Miss Rothschild says.

Gilbert Jr. was jobless - and seemed to have few prospects, and little interest, for finding serious work.

Instead, he spent most his time in the Hamptons, going to the gym, doing yoga and surfing.

'How could a guy be that gorgeous, that wealthy, that fit and kill his dad? This is the last thing in a million years that I thought he could do,' Miss Rothschild, 49, told the Post.

His one professional aspiration was founding his own hedge fund - but he complained that his father wouldn't give him the seed money to start it, Miss Rothschild said.

Gilbert Jr. has an investment company registered to his $2,400-a-month Chelsea apartment - though it's not clear the firm has any assets under investment.

A fire ripped through the home, built in the 1800s, in the early hours in Sagaponack, New York

A gas can and rags soaked in gasoline were found yards from the historic house

Rumors spread that Gilbert Jr started the blaze but police have never identified him as a suspect

The home which was constructed in the 1800s was completely gutted by the flames overnight

Gilbert Jr. sent his mother Shelley (left) out to fetch him a sandwich so he could murder his father, according to police. Gilbert Jr.'s sister Clare (right) also admitted that her father could be controlling about money

The company is a called Mameluke Capital - mamelukes being 13th-century Muslim slave soldiers.

Miss Rothschild said Gilbert Jr. was also preoccupied with how controlling his father was over his money and was convinced that he could never do anything to gain his approval.

WHO IS TOMMY'S SOCIALITE EX? ANNA ROTHSCHILD'S COLORFUL PAST Tommy Gilbert Jr's ex-girlfriend, Anna Rothschild (pictured), revealed details of alleged killer's troubled life on the day he was charged with the murder of his 70-year-old multimillionaire father. 'He's very much a loner. His phone never rang. No one texted him or called him. The one time it rang in four months while we were together it was his mother,' the 49-year-old told the Post on Monday. The Manhattan socialite dated Gilbert Jr, who is 19 years her junior, for four months in early 2014 and last saw him at Christmas. It's not the first time Ms Rothschild's colorful love life has drawn her into the public eye. In October 2003, the former London-based interior designer claimed she was dating actor Alec Baldwin, WENN reported, but he laughed off rumors saying at the time that he was enamored with a 25-year-old trainee lawyer. Several years before, Ms Rothschild, who gave her age as 31 but would have been 35, spoke of her love for large diamond rings to The New York Times as she divorced her second husband. She told The Times that her first, stockbroker husband had given her a five-carat diamond ring from Harry Winston while the second, an English businessman, had trumped up a six-carat piece.'Personally, I would have preferred ten carats,' she said. She's been married at least twice and her registered address is a small rental on the Upper East Side. The 49-year-old is the founder of A. Rothschild & Co. PR company. On the firm's Facebook page, she describes herself as 'an MBA Columbia University graduate and one of the most sought after socialites on the Upper East Side, Ms. Rothschild owns one of the most reputable and successful Public Relations and Marketing firms in New York City'. The website for the venture appeared to be now defunct. The last event posted to the firm's social media pages was on July 30. According to court records, Ms Rothschild filed for bankruptcy in 2011 and 2013. In 2012, Ms Rothschild was praising the benefits of taking a car service to Greenwich, Connecticut because of the hot dating scene in the suburbanite clubs. She told The Post at the time: 'There’s so many guys! I don’t know which way to look.' In winter 2012, she was rumored to be dating Prince Lorenzo Borghese, made famous by season nine of reality show The Bachelor. The Italian royal, who actually hails from New Jersey and runs a pet-care company, threw a lavish New Year's Eve party with the socialite at a Park Avenue penthouse. Advertisement

'He talked a lot about his dad and how mean he was to him and how nothing was good enough,' she told the Post.

The Post reports that Gilbert Jr. suffered from severe obsessive-compulsive disorder and was off his medication when he the murder happened, according to police sources.

The first thing multiple acquaintances said of Gilbert Jr when asked to comment by Daily Mail Online on their fellow Princeton or Deerfield alumnus was the rumor that he'd burned down his one-time friend's house last summer.

Additionally a long-time resident of East Hampton and acquaintance of Gilbert Sr., who was a member of the upscale Maidstone Club there, also repeated the allegation.

The home belonged to Peter Smith Sr., a friend of the Gilbert family.

The Post reports that Gilbert Jr. had been friends with Peter Smith Jr. - but that they had fallen out over a girl.

The Post also claims that Gilbert Jr. Killed Smith's dog - but this was denied to Daily Mail Online by sources close to the events.

Three days after the fire, on September 18, Gilbert Jr. was arrested for violating an order of protection taken out by Smith Jr.

Peter Smith Jr, 32, declined to comment on the allegations and his sister, Bettina Prentice, did not respond to requests for comment.

Both the Gilbert and Smith families were members of the elite Maidstone Country Club. The 120-year-old establishment sits in the village of East Hampton and has sweeping ocean views along with a private beach, tennis house and 18-hole golf course.

Former golfers on the links included Jacqueline Kennedy's father, John Vernou 'Black Jack' Bouvier III, and socialite Edith Bouvier Beale, famed from 'Grey Gardens.'

The Post reports that Gilbert Jr. had been banned from the club after a fight there.

Southampton Police detective Lisa Costa told Daily Mail Online on Monday that the house was destroyed in an arson attack and that there were no injuries.

She refused to comment further with regards an ongoing investigation. No one has been charged in the alleged attack.

Southampton Fire Department refused to comment to Daily Mail Online on Monday.

Tommy Gilbert Jr was arrested at his home on Sunday night in the Chelsea neighborhood of Manhattan, following the fatal shooting of his father, the founder of hedge fund, Wainscott Capital.

The 30-year-old was being held pending arraignment and the law office representing him had no comment.

Police said Gilbert Jr. went to his parents' home on the East Side on Sunday afternoon and asked his mother to go out to get him some food.

About 15 minutes later, she got a 'bad feeling' and came back, said Robert Boyce, the chief of detectives for the New York Police Department.

'She found Senior on the floor with a bullet hole in the head,' Boyce said. 'She also found a gun resting on his chest with his left hand covering it.'

But Boyce said it was a staged suicide - his son was trying to cover up the killing.

Officers with a search warrant went to Gilbert Jr.'s apartment on the West Side, where they found magazines, loose bullets and a shell that matched the gun found at the scene, police said.

Authorities were investigating how he got the gun.

The Princeton graduate was upset that his weekly allowance had been cut back when he went to his parents' home in midtown Manhattan on Sunday afternoon.

A source told the New York Daily News that Mr Gilbert Sr had cut back Tommy's weekly allowance to $300 and threatened to stop paying his rent.

The Ivy Leaguer, who was a regular fixture at Manhattan's black-tie benefits with society beauties on his arm, reportedly slipped past the doorman and into his parents' building shortly before the alleged attack at 3.30pm.

Gilbert Jr lives in a one-bedroom apartment in Chelsea where, according to listings, guarantors were accepted on the $2,400-a-month rent.

Investigators were ciphering through the rubble for days after the fire to determine a suspected cause

Nearly 80 firefighters attended the scene in the Hamptons but could not stop the blaze through the building

The beautiful home was entirely destroyed by the blaze. No one has been charged with the suspected arson

This 2009 class photo from Gilbert Jr.'s Princeton days show a happier time for the accused murdere

Gilbert Sr's wife Shelley, 67, found her husband dead in the bedroom within minutes of the alleged attack and called 911, police said.

Gilbert Jr was then seen walking out of the building in Manhattan's Turtle Bay area covering his face with a hoodie around 3.35pm, the New York Daily News reported.

Police recovered a Glock 22 .40-caliber handgun from the scene.

At 10.30pm on Sunday, Gilbert Jr was arrested without incident at his apartment after NYPD officers dressed in riot gear chopped down the door and found him hiding inside.

Thomas Gilbert Sr started Wainscott Capital in 2011, growing the fund to a value of $200 million.

He attended Princeton and Harvard Business School before a 40-year career on Wall Street.

According to Wainscott Capital's website, he had extensive knowledge of the stock market, private equity, real estate and the fixed income market.

His son, Tommy Gilbert Jr, attended The Buckley school on Manhattan's Upper East Side from kindergarten until eighth grade. Tuition costs around $35,000 a year.

Pictured left to right: Jamie Prentice, Peter Smith, Bettina Prentice and Chris Smith pictured at an art benefit in October 2013

Party boy: Gilbert Jr was a fixture on the New York social scene with a host of beautiful women ready to pose for pictures with him including Arielle Patrick (left) and Maddie Haddon (right)

Social: Tommy Gilbert, pictured with friend Monika Plocienniczak, at the Young New Yorkers Summer Party in the Hamptons

Noteable alumni of the school include actor James Harder, philanthropist David Rockefeller Jr and Robert Wagner, former deputy mayor of New York.

How could a guy be that gorgeous, that wealthy, that fit and kill his dad? This is the last thing in a million years that I thought he could do. Anna Rothschild, Gilbert Jr's ex-girlfriend

He then went on to the $50,000-a-year Deerfield Academy in Western Massachusetts, which counts the King of Jordan and Prince of Jordan among its alumni.

After graduating from Deerfield in 2003, Gilbert Jr accepted a place at Princeton University where he graduated in 2009.

A friend told Daily Mail Online on Monday: 'He was a really nice person. He was smart, athletic and he went to Princeton.

'He took some leave of absences from Princeton which is why it took him so long to graduate. He must have been really angry to do something so out-of-character.'

Society friends: Alex Brice, Amy Poliakoff and Tommy Gilbert pose together at Greensward Circle's 7th Annual 'Evening in the Garden' in June 2012

Parties: Tommy Gilbert, far right, pictured with Charlotte Morse, Matthew Vahidi, Alexandra Chemla and Emma Greenberg at the Parrish Art Museum Midsummer Party in the Hamptons in 2012

A classmate, who attended Deerfield with Gilbert Jr, also said: 'Tommy was my classmate. This story is an incomprehensible tragedy. My heart goes out to the entire Gilbert family.'

Details of Gilbert Jr's profession remain unclear but he was photographed on multiple occasions at black-tie society events.

The 30-year-old was pictured in March 2014 at the School of American Ballet's winter ball with Arielle Patrick, a 2012 Princeton grad, child of Manhattan private schools and now a PR director, who sources told the Daily Mail Online that he had dated.

Miss Patrick refused to confirm whether the pair had dated on Monday.

A fellow Princeton graduate told Daily Mail Online that Gilbert Jr was a 'highly disturbed individual'.

Police remove a body bag from the luxury Manhattan apartment building late on Sunday where a multimillionaire hedge-funder was found with a gunshot wound to the head

The NYPD broke down the door of Gilbert Jr's West 18th St ground-floor apartment (pictured) to arrest him on Sunday. According to published news reports, Gilbert Jr had his allowance cut back by his father who was paying his $2,400-a-month rent

Friends in the 30-year-old's circle told Daily Mail Online that he loved surfing, was 'handsome and nice' but extremely quiet and never talked.

The Gilbert family property is a $6,000-a-month rental apartment at 20 Beekman Place on 50th Street, a few blocks north of the United Nations on the east side of Manhattan.

Mr Gilbert Sr also owned a property in the Hamptons which was listed for sale at $11.5million.

The 2.5 acre-property has five bedrooms, four baths, a heated pool and screened in porch and sits in one of the area's most exclusive enclaves.

Wainscott Capital avoided losses which plagued other hedge funds in October last year, gaining 1.65 per cent that month.

Thomas Gilbert Sr owned this $11.5 million property in the Hamptons which is set in 2.5 acres of land