Just after 3 a.m. on Monday, a semi truck collided with two other vehicles on Freeway 60 near Pomona, California, leaving two victims dead and another two injured.

The trucking accident took place between the Chino Valley Freeway and Reservoir Street.

According to police involved in the investigation after the accident, the two cars had both pulled over onto the right shoulder of the freeway because one of the vehicles had run out of gas, and the other was attempting to help. At this time, the semi truck apparently swerved into the shoulder and hit the two people who were out of the car. The crash then resulted in the semi overturning, and started a small fire to further complicate matters.

One man and one woman were killed in the accident, with one of the victims falling off the overpass to the road below, which was Gary Road.

As a precaution, the semi truck driver was taken to a nearby hospital for monitoring. California Highway Patrol officers say they are not sure if alcohol or drug intoxication is a factor in the accident, but that they are still investigating whether this is the case.

As a result of the collision, an alert was issued and all eastbound traffic lanes were shut down due to the accident. Traffic didn’t open for normal movement until nearly 7 a.m., almost four hours after the initial impact.

Once again, the severity of the accident shows how dangerous semi trucks can be to other people on the road, even those not actively driving. The shoulder is supposed to be a relatively safe place someone can change their tire or stop in the event of an emergency, but all it takes is one negligent semi truck driver to turn it into a very dangerous place to be indeed.

The names of the victims in the crash, along with the name of the driver, have not yet been released.