An armed man or woman appointed to patrol a grounds or campus for security purposes would be called a shomer or shomeret.
Historically, shemira was a form of guard duty, to prevent the desecration of a body prior to burial.
[7] Shomrim are prohibited from eating, drinking, or smoking in the shemira room out of respect for the dead, who can no longer do these things.
Shomrim are allowed to be paid, as this mitzvah is not benefiting from the dead, but helping to relieve the burden of the relatives whose duty it is to guard the body.
[9] In some communities individuals are paid to do this, while in others it is done on a volunteer basis, often by friends of the family of the deceased or members of a chevra kadisha, Jewish burial society.