IIRC, I walked in on a fight between the owner of the high rise bar in DC and some other guy, and afterward, the owner wanted me to help with something. He deals in smuggled drugs (to get around the import tax or something like that), but there's some other issue in there (it's been a while, the memory's fuzzy). Along the way you go take out a deal at one of the bridges, and interrogate a female ghoul, who will eventually give up the location of the drug factory. Afterward, the owner decided he didn't want a witness, so he tries to shoot her, and I'm left having to kill him because I said she could go. She did die, though. Later, the father of one of the guys I had to shoot got my attention and asked me about it, I used my Charisma to lie and said Marowski did it, so it's off to Goodneighbor to deal with him for payment from the father who wants revenge for his son. Strangely, despite a lack of witnesses, Marowski knows what I did, and tried to get 2000 caps from me as payment for the harm I caused him. Can't just attack Marowski at his desk in the hotel, so I waited until the middle of the night, snuck into his room, closed the door, and removed his head from his body with a laser pistol at close range. Piper, of course, was not amused by this, though it kept us both from being killed or forking over a bunch of caps. Besides, Marowski was a bad guy, the son was bad, and it was all bad for the Commonwealth.
Bonus quest bugs: I still can't get rid of the Miscellaneous quest to pay Marowski 2000 caps, despite him being quite dead. And the bodies of the people I attacked by the river are still there, continuously restocking their loot, so every once in a while I go through the area and grab some more stuff to sell/salvage.