TORONTO -- Police have laid additional impaired driving charges in connection with a horrific collision in Brampton, Ont. that claimed the life of a mother and her three young daughters back in June.

Karolina Ciasullo, 37, and her three daughters – Klara, 6, Lilianna, 3, and Mila, 1 – were killed shortly after noon on June 18 when their Volkswagen Atlas was struck by a blue Infiniti G35 near Torbram Road and Countryside Drive.

The driver of the Infiniti, later identified by police as 20-year-old Brady Robertson, was taken into custody one week later and charged with four counts of dangerous operation of a motor vehicle causing death in connection with the crash.

He was also charged with one count of dangerous operation of a motor vehicle in connection with another collision that took place two days prior to the one that killed Ciasullo and her daughters.

In a news release issued on Friday, Peel Regional Police announced that they have now charged Robertson with four additional counts of impaired operation causing death by drugs in connection with the June 18 crash.

Robertson was previously denied bail on the earlier charges during a court appearance in August.

He has been held at the Maplehurst Correctional Complex in Milton, Ont. since his arrest.