Surprise police said a boy pulled a knife on his mother who refused to let him go trick-or-treating as a "gay Justin Bieber," the singer and teen idol.

The 12-year-old boy had been grounded Halloween night after an argument with his mother, who said his costume idea was disrespectful, police spokesman Sgt. Mark Ortega said.

After throwing a tantrum and getting grounded from trick-or-treating, he grabbed a knife from his room and threatened to kill her, Ortega said.

The mother disarmed her son without injury and called police.

Police arrested the pre-teen on suspicion of threatening his mother with a knife.