MADISON, Wis. (AP) — The operator of the Wisconsin brewery where an employee opened fire on co-workers last week says someone years ago placed a noose on the gunman’s locker.

Anthony Ferrill gunned down five co-workers at Molson Coors’ brewery in Milwaukee before killing himself last week. His motive remains unknown.

Ferrill was black. Four victims were white and one was Latino.

Local media have reported on speculation that the shooting was racially motivated. Spokesman Adam Collins says there’s no evidence to suggest that any shooting victims were involved in the incident.

Police say it’s too early to conclude racism factored into the attack.