Interesting question re: gun free zones
There was some argument regarding whether a private entity which forbade firearms in an area, or in parked cars, might assume some liability to a person who became a victim of crime because they could not defend themselves. The usual counter was the concept that a person generally has no legal duty to protect someone else from crime -- phrased otherwise, to prevent someone else from committing a criminal act.
Reader CarlS points out an interesting passage in DeShaney v. Winnebago County Department of Social Services, 489 U.S. 189 (1989). The suit was brought on behalf of a boy who suffered serious brain damage when county social workers ignored evidence that his father was beating him, and the Supremes held that this did not involve deprivation of liberty without due process of law.
In the course of distinguishing cases that allowed prisoners to sue for lack of safety and medical care, the majority noted:
"The affirmative duty to protect arises not from the State's knowledge of the individual's predicament or from its expressions of intent to help him, but from the limitation which it has imposed on his freedom to act on his own behalf. See Estelle v. Gamble, supra, at 103 ("An inmate must rely on prison authorities to treat his medical needs; if the authorities fail to do so, those needs will not be met"). In the substantive due process analysis, it is the State's affirmative act of restraining the individual's freedom to act on his own behalf -- through incarceration, institutionalization, or other similar restraint of personal liberty -- which is the "deprivation of liberty" triggering the protections of the Due Process Clause, not its failure to act to protect his liberty interests against harms inflicted by other means."
So the State's liability in the prisoner context does not arise from its knowledge that the prisoner is in danger, but from the fact that it has limited his freedom to protect himself...