Ryan Lawrence, 25, indicated that he was jealous because everyone was concerned about his daughter, Maddox, while she battled eye cancer, which she survived.
He has pleaded guilty to killing her, burning her body and the bat he used to beat her in a fire pit for three hours, then anchoring her remains with cinder blocks and dropping them into a Syracuse creek, reports WRGB-TV.
An Amber alert was issued in February when Lawrence and Maddox vanished. The toddler's body was found by police divers about 36 hours after she was first reported missing.
Lawrence told police he prayed to God to give him a sign if he shouldn't go through with what he planned.
"God, if I'm not meant to kill her, make her stumble," Lawrence thought, according to what he later told Detective Mark Rusin.
Then he hit her in the back of the head with a baseball bat, Lawrence confessed, according to Rusin.
Lawrence pleaded guilty to first-degree murder and will be sentenced from between 25 years to life in prison as part of a plea deal.
Maddox's mother, Morgan Lawrence, sobbed as County Court Judge Anthony Aloi read a detailed description from the indictment of what Lawrence did to his daughter when he killed her.
Lawrence also appeared to tear up and breathed heavily as he said "guilty." He will be sentenced in October.
Onondaga County District Attorney Bill Fitzpatrick called Maddox a "fighter" who had beaten back illness. A makeshift memorial of stuffed animals and candles on the banks of the Onondaga Creek may become the site of a permanent memorial site for the little girl.
The family hopes to have a new bench, a sign and plaque and an area with flowers as a memorial to Maddox.