I think on this one I side with the police and the Kelly's, the owners of the Scotriders school.

In Ontario there are a few farmers raising roe and fallow deer for meat and they say the bucks can get quite dangerous.

It might not seem like it because they are not large but they get to thinking of humans as rival bucks and want to spar with their antlers for control of territory and the does.
This buck was at about the right age.

One of the things about roe bucks is that they tend to approach slowly and try to engage as if you had antlers too.
They feel with their antlers until they have contact and then they thrust just as hard as they can, just like they would with another buck.
If you didn't know what their game is you might not realize they were attacking until you were getting gored.