Moreau was the driving force behind recently adopted pension-reform legislation that has angered municipal employees and sparked widespread protest.
The 45-year-old man was arrested in nearby Terrebonne on Monday after a woman filed a complaint with the local police force.
Montreal police spokesman Jean-Pierre Brabant confirmed Thursday the officer is an employee of the force.
Terrebonne police Capt. Sylvain Theoret said in an interview authorities met the woman, 40, and then questioned three others, including two minors.
The names of the minors — boys aged 12 and 14 — are covered by a publication ban.
"Following those meetings and after taking statements, we proceeded to arrest the suspect," Theoret said.
"Since that time, the suspect has been detained in Saint-Jerome."
Theoret said the officer was located by tracking down his vehicle and added he did not resist arrest.
The charges include criminal harassment, uttering death threats and mischief and are related to events that allegedly occurred over a nine-year period between 2005 and last Monday.