If they are close together at a busy time then they must have been under three minutes inbetween them. Just being close, however, is not enough evidence to say that he definetly was breaking NLR so you cannot warn him right away just from the logs. If Player x can provide good evidence that Player y did break NLR (For example, a short video that shows a gangster killing a cop to safe his fellow gangster friends from being arrested/killed. NLR is three minutes so if Player y has not forgotten his past life and could have also possibly stepped into the same district within the three minutes and has now broken the NLR, so I would proceed to warn him/her. If not enough evidence was shown, Player y will just be let free.