Plotkin stepped over the line with cleaning contractors, four sources say. (Astrid Riecken/For The Washington Post)

But just what prompted the station Thursday to announce a “parting of ways” with an unsentimental three-line statement? That we didn’t know.

The skinny: It wasn’t a newsroom blowup. It was a lobby blowup. According to four sources, Plotkin chewed out the small crew of Latino workers who perform cleaning services at WTOP’s office building.

The trouble started three days earlier, on Jan. 23. That afternoon, Plotkin rolled into the lobby of the building at Wisconsin and Idaho Avenues NW that houses WTOP. There were power troubles at the building and the lobby was dark. The D.C. statehood champion was trying to get upstairs to the radio station’s offices but ran into obstacles: The door to the stairwell wasn’t opening, not a good situation for Plotkin — a stairs guy all the way. He then walked into an open elevator, only to find that it was out of service.

So he raged, according to the sources (including eyewitnesses) — all swear words and nastiness, directed at a cleaning crew that just happened to find itself in Plotkin’s line of fire. As it turned out, one of the elevators was in working order.

The explosion wasn’t enough to trigger a complaint by the cleaning crew. It carried on as usual, until the next afternoon. That’s when Plotkin took to yelling at a cleaning crew member again, this time just outside the building’s doors, the sources say. Exactly what had provoked Plotkin this time isn’t clear. Following the encounter, a representative of the team approached WTOP to apprise the station of its issues with Plotkin.

WTOP news chief Jim Farley declined to comment on the goings-on. A call to the cleaning contractor has gone unreturned. Likewise messages left on voice mail at Plotkin’s home.

The sequence of events suggests that WTOP could handle Plotkin exploding at fellow journalists; tolerating the mood swings of highly talented and mercurial individuals, after all, is a specialty of any good news organization. Yet when Plotkin took to screaming at the people who pick up after him, the radio station apparently decided that a line had been crossed.