The son of a millionaire Manhattan hedge fund founder who allegedly gunned down his dad over his allowance has been arraigned on a second-degree murder charge, authorities said.

Thomas Gilbert Jr., 30, was also charged with criminal possession of a weapon and criminal possession of forgery devices in the Sunday killing of his 70-year-old father.

New York City police said Thomas Gilbert Sr. was shot in the head at his Beekman Place residence on Manhattan's East Side Sunday afternoon after the two argued over the son's allowance. 

They say the son went to his parents' home and asked his mother to go out to get him some food. About 15 minutes later, she got a "bad feeling" and came back, Robert Boyce, the chief of detectives for the New York Police Department, told the Associated Press. When she returned, police say she found her husband on the floor with a bullet wound in the head and a handgun near his body.

A law enforcement source told the New York Post that Thomas Gilbert Jr. had just been told by his father that he would only receive $400 for spending money per month from that point on in addition to $2,400 per month for rent. The younger Gilbert had previously received $600 per month.

"She [Mrs. Gilbert] found Senior on the floor with a bullet hole in the head," said Boyce. "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 found magazines, loose bullets and a shell that matched the gun found at the scene in Gilbert Jr.'s apartment, police said. Authorities were investigating how he got the gun.

The defendant is due back in court on Friday. His attorney didn't immediately return a call for comment.

A neighbor told the paper that he had learned from a doorman that the younger Gilbert had entered the building shortly after his father, but left minutes later and did not respond to the doorman's greeting.

In 2011, the elder Gilbert founded Wainscott Capital Partners Fund, which has $200 million in assets. Industry publication Hedge Fund Alert said in an August 2013 article that the fund had a net return of nearly 25 percent in 2012.

He was a graduate of Princeton University and Harvard Business School. Gilbert Jr. also attended Princeton, graduating in 2009 with a degree in economics. Authorities said he had no recent work history.

Gilbert Sr. worked on Wall Street for more than 40 years, according to his profile on Wainscott's website, and previously co-founded Syzygy Therapeutics, a biotech asset acquisition fund. He also was founder and CEO of an online teacher-education company called Knowledge Delivery Systems Inc.

Wainscott had no immediate comment Monday. The hedge fund invests in biotechnology and health care stocks, which typically make up about 70 to 80 percent of its investments, according to the firm's website. The fund focuses on stocks traded on large exchanges like the Nasdaq and New York Stock Exchange, with as many as 70 different investments at one time. The minimum amount for investors is $500,000.

"He was a pillar on Wall Street — somebody everyone looked up to," Hector Torres, a neighbor of Gilbert's who also works in finance, told the New York Post. "Very nice gentleman ... They seem like a normal family," Torres added. “Every time I saw him in the elevator, he would say hi, he would ask how I was."

The younger Gilbert has a pending criminal case in the town of Southampton, on eastern Long Island.

Gilbert was arrested Sept. 18 on a charge of criminal contempt. Southampton town police say he violated an order of protection issued in Brooklyn in June. He has pleaded not guilty and has a Feb. 2 court date scheduled.

The Associated Press contributed to this report.