Federal authorities initially used that language Monday when talking to state officials about the actions of a Maine driver who was fatally shot by immigration officers. In public statements, Department of Homeland Security officials shifted their description to say officers fired into the vehicle “fearing for public safety.”

It was the second time in a week that federal immigration authorities shot and killed someone behind the wheel of a car, initially accusing the driver of attempting to ram into immigration officers.

But while the weaponization of a car is often used to justify the use of deadly force against a driver, the legal definition is a lot less clear cut.

State legislatures and some courts say cars can be considered weapons

In numerous state and federal courts, judges have agreed that vehicles can be considered weapons when they are used to inflict harm. But many of those cases have been considerations of whether enhanced charges such as aggravated assault with a deadly weapon can be levied against a person after an injury or death was already caused by a vehicle.

Many state laws that address assault with a vehicle are designed to enhance manslaughter or other charges against people violating traffic laws or driving requirements. Judicial opinions have largely focused on crimes of negligence, road rage or driving while intoxicated, and in rare instances, cases where someone purposefully drove their car into a crowd of people.

They rarely deal with the question faced by police or federal law enforcement officials of when a moving vehicle should be considered a dangerous weapon, and when that allows for the use of deadly force.

Training often says to move rather than shoot

Many law enforcement departments and agencies weigh the potential for unintended harm heavily when instructing officers or agents on when it’s acceptable to fire a weapon at a moving vehicle.

Many department policies tell officers to move out of the way of a vehicle rather than shoot because of the potential harm to bystanders who could be struck by unintended gunfire or by a careening vehicle if the driver is incapacitated.

Policies often say a suspect fleeing is not enough justification for using deadly force. Some require another weapon such as a firearm being used as a threat from the person in the vehicle to establish a clear threat to public or officer safety.

Experts say many factors determine when a car is weaponized

Exceptions exist in many use-of-force policies for what became a familiar scene abroad and at times in the U.S. — a person driving a vehicle into crowded public streets to inflict as much damage as possible.

But, experts say those exceptions have been used as a defense in situations where a person was not posing the same level of threat.

They say officers and juries should consider factors such as the speed of the vehicle, whether there are large gatherings of people on the sidewalks or nearby, and the reason for the initial police interaction. For example, a person fleeing an armed robbery at a bank might pose a higher danger than someone fleeing a traffic stop.