A fourth suspect wanted in connection with a robbery in Barrie has been arrested.

Toronto police arrested 21-year-old Ashtoney Thompson on Wednesday for an unrelated matter.

Police believe he is the fourth suspect in a robbery near College Heights Park on September 17. 

Police say four suspects robbed two people around 4 a.m. at the Duckworth Plaza.  Two teenage girls and a 21-year-old man have already been arrested as part of this investigation.

The Special Investigations Unit has been called to investigate after they say a Barrie Police officer discharged his firearm while in pursuit of the fourth suspect.

The SIU is called to investigate any incident involving an Ontario police officer and a member of the public that results in death, serious injury or an allegation of sexual assault.