An allegedly armed woman was struck and killed when she ran onto the 57 Freeway in San Dimas on Monday night while fleeing from authorities. 

It began when Los Angeles County Sheriff's Department deputies were called to the area for reports of a woman armed with a gun, according to the department. 

When they approached her, she allegedly took off running and began trying to cross southbound lanes of the freeway near Arrow Highway, deputies said. 

A little after 10 p.m., she was struck by an SUV and despite attempted life-saving measures by deputies, she was declared dead at the scene. She has not yet been identified. 

California Highway Patrol officers issued a SigAlert for three southbound lanes due to the collision, which lasted until just after midnight.