Thompson died of complications from cancer, his office said on Sunday.
The officer is scheduled to be sentenced on April 14.
Prosecutors say the alleged victim's father committed incest.
Liang's conviction last night wasn't delivered by the district attorney. It was the product of thousands of New Yorkers clogging city streets. It was demanded at every march and vigil where his family, friends and supporters would lift his name.
December: Donovan Allen, who falsely confessed to the murder of his mother in 1990 at the age of 18, is exonerated by DNA
The toy rifle that little Naquan had that night, which was perfectly legal and could be bought at any toy store in 1994, had bright orange coloring and was not shown by Hynes. Recently, in a case eerily similar to the Heyward shooting, a judge recommended that charges be brought against the Cleveland police officer that shot and killed 12 year old Tamir Rice.