PLAINFIELD, N.J. (AP) _ A police officer shot himself to death Friday as he was being questioned by investigators following his arrest on aggravated sexual assault charges, police said.

Officer Kenson B. Simon, 26, was pronounced dead at of a self-inflicted gunshot wound at police headquarters, said Plainfield police Lt. John Driscoll.

''He had apparently secreted an unauthorized personal weapon under his shirt,'' Driscoll said. ''While he was in the private office being interviewed ... by an investigator he suddenly drew the weapon and killed himself with a single shot,'' said Driscoll.

Police took away the officer's service weapon before his arrest on sex assault charges, Driscoll said. The lieutenant would not elaborate on those charges.

Simon, assigned to radio car patrol, had been a department member for 1 1/2 years.

Union County prosecutors and Plainfield police were investigating.