A 55-year-old Brooklyn man has pleaded guilty on the eve of his trial to manslaughter for stabbing a Queens man to death with an ice pick more than two years ago, prosecutors said Thursday. 

Norbert Williams, of Bedford-Stuyvesant, knocked on Joseph Smart's apartment door in Far Rockaway in the middle of the night June 18, 2017 and said he needed help. He said he was being harassed. Barefoot and wearing just shorts and an undershirt, Smart rushed to help him. The two walked into a stairwall. 

Then, suddenly, Williams attacked Smart, prosecutors say. Smart was stabbed around 30 times, suffering a puncture wound so deep that a piece of the ice pick broke off and got stuck in his spine, authorities have said. Williams was wearing glasses and boots at the time of the attack; Smart's blood was on them. 

Prosecutors haven't given a motive for the attack. Williams pleaded guilty to second-degree manslaughter hours before jury selection was to begin. He is expected to be sentenced to 24 years in prison early next year. 

"Early one morning, the defendant asked the victim to help him out and once inside the apartment building’s stairwell, he pounced on the man with an ice pick," Acting Queens District Attorney John Ryan said in a statement. "The victim was stabbed dozens of times in the head, neck, back and torso. This was a rage-induced stabbing frenzy that is wholly unacceptable. The defendant has now admitted to this heinous crime and is facing a lengthy term of imprisonment when sentenced."