I picked a vehicle key from my driveway and aimed it at the walker
Do you have a reason for aiming the vehicle key?
I was practicing my aim by picking it up and aiming it.
Even if you were only practicing, it is good to acknowledge that you did that to the walker. People will be more understanding if they see you aiming at it.
They won't be mad if they know why I did it.
Maybe you can explain it to them if asked. It is acceptable to take responsibility for your actions.