Per a report from the Guardian, no motive has been determined. The incident occurred Friday morning, with witnesses describing scenes of evacuated employees "pouring out" of the building and into the streets. "Everybody starting pouring out and running towards the square around the back," one witness said, adding that they later saw a "young white man with a red jacket" tacked by security. That person was later arrested.
"No evidence of any firearms involved in this incident," a police rep later confirmed in a statement. "It is not being treated as terror-related."
A label rep later said that the incident is believed to have been the result of a "violent altercation" between "members of the catering team," though police have not gotten this specific with their wording. "The incident is now in the hands of the Metropolitan Police," a Sony Music UK rep said.
This post may be updated as new information becomes available.