http://hsjcc.on.ca/wp-content/uploads/Police-Powers-Under-the-MHA3.pdf

https://www.cmhak.on.ca/images/Form2_Navigation.pdf

Section 17 is what POs use in emergencies.

With a called in complaint from OP, they can do what's called a Form 2 from a JP.

Justice of the peace’s order for psychiatric examination 16 (1) Where information upon oath is brought before a justice of the peace that a person within the limits of the jurisdiction of the justice,

(a) has threatened or attempted or is threatening or attempting to cause bodily harm to himself or herself;

(b) has behaved or is behaving violently towards another person or has caused or is causing another person to fear bodily harm from him or her; or

(c) has shown or is showing a lack of competence to care for himself or herself,

and in addition based upon the information before him or her the justice of the peace has reasonable cause to believe that the person is apparently suffering from mental disorder of a nature or quality that likely will result in,

(d) serious bodily harm to the person;

(e) serious bodily harm to another person; or

(f) serious physical impairment of the person,

the justice of the peace may issue an order in the prescribed form for the examination of the person by a physician. R.S.O. 1990, c. M.7, s. 16 (1); 2000, c. 9, s. 4 (1).