proceeding

He had often painted himself at a mirror, a tortuous and fascinating proceeding, as every artist knows, and had been forced to admire the way in which he was made.

I had occasion […] to make a somewhat long business trip to Chicago, and on my return […] I found Farrar awaiting me in the railway station. He smiled his wonted fraction by way of greeting, […], and finally leading me to his buggy, turned and drove out of town. I was completely mystified at such an unusual proceeding.

an illegal proceeding

Since impeachment is a legal proceeding, while anyone can make a motion to start the process, the Judiciary Committee determines whether there are sufficient grounds for impeachment.