Princeton graduate Thomas Gilbert Jr.was sentenced Friday to 30 years to life in prison after shooting and killing his wealthy father in 2015 following a dispute over his weekly allowance.

Gilbert Jr., 35, was convicted three months ago in the killing of his 70-year-oldfather at his parents' home on Manhattan's East Side. The jury rejected the defendant's insanity defense during the trial.

The younger Gilbert was reliant on his parents for basic daily expenses and had been unable to hold down a job, prosecutors said.

He received a weekly $1,000 allowance from his parents — which the defendant spent on travel and other personal expenses. That allowance had been cut prior to the killing.

Gilbert Sr. reduced his son's allowance to $300 hours before the shooting, prosecutors said, according to a CNN report. Gilbert Sr. was the founder and manager of the New York-based Wainscott Capital Partners Fund.

In a victim impact statement, the victim's wife, Shelley Gilbert, asked for Gilbert Jr. "to be given as light a sentence as possible,"according to CNN. She said the family had been seeking medical help for the defendant for years because "he's too sick to be able to judge."

The jury found that Gilbert Jr., who was also convicted on charges of criminal possession of a weapon, murdered his father with a shot to the head at close range. The weapon, a semi-automatic pistol, was purchased months earlier from an Ohio seller.

The defendant put the gun in his father's hand in an attempt to stage the death as a suicide, according to trial testimony.

"Thomas Gilbert Sr. was a beloved member of his family and business community when his own son murdered him in a cold-blooded killing," District Attorney Cyrus Vance said Friday in a statement. "But now, thanks to my office's prosecutors, the defendant has finally been held accountable and he will serve a life sentence for this unconscionable crime."

Contributing: The Associated Press