They already visited him at home once without a violent altercation, but they needed a body to satisfy their bloodlust.

They already visited him at home once without a violent altercation, but they needed a body to satisfy their bloodlust.

The tactics used were clearly used to cause an altercation. If an arrest needed to be made, arresting him outside the home when he was in a public place, e.g. a parking lot, was far less likely to result in injury or death.
There was no need to arrest him at his home, as the alleged threat he made could not have been carried out without leaving his home. Thus, surveillance was sufficient to avoid any contemplated crime pending an arrest.