(CNN) Thomas Gilbert Jr., who was convicted of killing his father after the older man cut back his weekly allowance, was sentenced Friday to 30 years to life in prison.

Thomas Gilbert Sr., a founding managing partner of the hedge fund Wainscott Capital, was found dead in his apartment in January 2015 with a gunshot wound to the head.

Gilbert's attorneys did not dispute that he killed his father but said he was not guilty by reason of insanity. Jurors in June dismissed the insanity defense and convicted him of second-degree murder. They also found him guilty on two counts of criminal possession of a weapon in the second degree. He was found not guilty of criminal possession of forgery devices.

Shelley Gilbert, the victim's wife, gave a victim impact statement Friday where she said the family wanted Gilbert Jr. "to be given as light a sentence as possible."

"As I've said many times in court, we've been trying to get Tommy into a hospital for 15 years," Shelley Gilbert said. "He's too sick to be able to judge. He needs to be in a hospital, had he been so my husband would still be alive."

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