Does a prison officer's witnessing of an argument between two inmates constitute actual knowledge of a substantial risk of harm?

Further, one inmate's threat against another inmate will not serve to impute actual knowledge of a substantial risk of harm where neither inmate has a prior history of violence. Id.; see also Perkins v. Grimes, 161 F.3d 1127, 1130 (8th Cir. 1998) (no notice of the risk that an inmate would sexually assault another where they had previously been housed together without incident); Lucas v. Eagleton, 2007 WL 2457571 at *9 (D. S.C. 2007) (a prison official's witnessing of an argument between two inmates did not put the official on notice of a risk of harm absent evidence of a propensity of violence or a "history of animosity").