What object did Parris see as an intentional threat to his life?

In Act IV, Parris comes to the court trembling and afraid.
Apparently, when he was using the door to his house a dagger
fell:

Tonight,
when I open my door to leave my house - a dagger clattered to the ground... There is
danger for me. I dare not step outside at
night.

This quote proves
Parris' justified fear of the people. In fact, it causes him to go to a great risk. He
pleads with the judges to not hang this "sort" meaning well-respected and highly revered
people of the society. Parris believes that this dagger was just a threat, but that the
terror intended will further infect him and that someone may indeed take a greater stab
at ending his life.