If they do not have a 'special relationship', such as being assigned to guard someone, then they are not guilty of a federal crime for not protecting them. However, there could be state law or it could be a violation of contract for which they could be sued.

The school district and sheriff’s office in the Florida county that is home to Marjory Stoneman Douglas High School had no constitutional duty to protect the students there during the deadly February massacre, a federal judge has said in a ruling. The decision was made in a lawsuit filed by 15 students who said they suffered trauma during the Feb. 14 attack in Parkland, Fla.