In section 1983 action alleging that defendants-police officials used excessive force by deploying tear gas and flashbang grenades in attempt to gain access to plaintiff's apartment after plaintiff had notified police that he had gun and threatened to kill himself, Dist. Ct. did not err in admitting evidence of plaintiff's psychological profile, as well as fact that plaintiff was facing potential 5-year prison sentence for recent substance abuse violations, even though defendants were not aware of said evidence at time of incident. Plaintiff's estate had opened door to introduction of said evidence by introducing evidence of plaintiff's mindset, and thus disputed evidence was relevant to counter estate's evidence that plaintiff was in good spirits near time of incident. Dist. Ct. did not err in granting judgment as matter of law on qualified immunity grounds as to defendant-police commanders with respect to their decision to use tear gas and flashbang grenades, where no case law precluded use of either device under circumstances where plaintiff posed danger to others. Fact that defendants used 12 times incapacitating level of tear gas did not require different result where plaintiff was still functioning within apartment. Finally, Dist. Ct. did not err in granting summary judgment with respect to defendants who shot and killed plaintiff where one defendant testified that he was in fear of his own life when plaintiff pointed gun at him.