I would be surprised if terrorists killed more people. That isn't to say that terrorism should be taken lightly because they could get "lucky" and kill lots of people. While a scary issue, due to the proximity of the US (minus local terrorists like the alt-right groups) we are largely shielded from it. Hell drunk drivers kill passengers and those in other vehicles every year far more than terrorism has minus in 2001.
I wonder how many police officer killings are due to "suicide by cop".
I wonder how many police officer killings are due to "suicide by cop".