Police tried to step in to stop the mobs, but were attacked themselves.
The argument
The argument rests on an account of what the police actually did at the scene. Police tried to stop the lynching, but were instead attacked by the mob and could not save the victims. The distinction it presses is between failing to prevent an outcome and being party to it: an officer who is present and does nothing is open to the charge of complicity, whereas one who intervenes and is driven off is not. The evidence is the force's own account of the incident. A statement released by the local police stated that "one of our patrolling vehicles later spotted the severely injured trio lying on the road and stopped to investigate. However, our team was also attacked by the mob and the vehicle pelted with stones. Our personnel had to flee and were unable to rescue to the victims". Several details in that statement bear directly on the allegation. The patrol stopped rather than passed by, which is an act of intervention rather than of avoidance. The mob then turned on the officers themselves and stoned their vehicle, which is not how a crowd behaves towards participants it takes to be on its side. And the officers withdrew only after being attacked, in circumstances where remaining would have meant facing a crowd they were far too few to control. The conclusion follows from the incompatibility between that sequence and the charge being made. Complicity requires either participation in the killing or a decision to stand aside while it happened, and what the statement describes is neither: an attempt to intervene, defeated by the same violence that killed the victims. They clearly were not complicit; they were just, sadly, unable to save the victims.
Premises
Counter-arguments
The police did not try to stop the lynching. Video of the lynching shows the police letting it happen, and police were then suspended over the incident.
Rejecting the premises
[Rejecting P1] The premise rests on the account of the force whose conduct is in question. Footage of the incident was read as showing officers present while the attack went on, and personnel were subsequently suspended over it — which is not what an account of a thwarted rescue would predict. [Rejecting P2] Being outnumbered would explain a failure to rescue, but the allegation concerns what happened before that point: whether the crowd was dispersed when it could have been, and whether the men were left to it. Withdrawing under stones does not answer either question.