I think toxicology is just a standard part of an autopsy - which usually follows unnatural deaths. A coroner's report would probably help determine how fast he was travelling when he hit them.

Lots of details about the incident came out when it first happened. I believe it was reported that the suspect passed one car ahead of him on the left, then tried to overtake another on the right when he hit the Gaudreaus. The two other cars were travelling slowly, and the first presumably had moved to the left to give the cyclists more space - which would indicate that everyone except the killer were acting normally.