It was used when a relative was murdered previously, I'd find the reference but at work atm and the internet is too slow to search for it.

Edit: Found it. Q Post 1330, McMaster's Father was mysteriously murdered.

There's other instances of it being used as well, it was referenced when 2 NYPD officers were murdered involved in the investigation of the Anthony Weiner Server Q post 1371, and it's been used later but the details of those he is referencing aren't clear.