Since Jan. 1, there have been at least 350 incidents of gun violence in the United States in which four or more people were killed or injured, according to the Gun Violence Archive.

Nine of those incidents took place in Missouri, including the murder of four people in February in Clay County.

On Monday, Columbia-based law enforcement and emergency responders tested their ability to respond to a mass shooting. Using Laws Hall, an empty University of Missouri dormitory slated for demolition early next year, the agencies organized a command post, sent officers in to search for the shooter and treated victims.

Sarah Stone, who took time from her job in the Department of Student Life and Campus Activities to play the part of victim, said she was told she was uninjured and needed to help the wounded and be prepared to give a description of the suspect. The experience was scary even though she knew it would happen.

“He came in and he’s like, ‘I’m going to fire these blanks. I’m going to fire them,’ Stone said. “So we knew, but just hearing it is always kind of freaky, and nobody wants to be in a room with a gun.”

The Columbia Fire Department, the Columbia Police Department, the University of Missouri Police Department, the Boone County Sheriff’s Department, the Missouri State Highway Patrol, Boone Hospital Center and University Hospital took part in the drill.

The active shooter training began with a simulated emergency call. The plan was not to test response times, fire department Battalion Chief Brad Frazier said, but to evaluate how well agencies work together.

“This exercise is really to test our capabilities, our inter-operability,” he said. “We work together one-on-one, with each agency one-on-one, on an almost daily basis, but to get them all together at the same time is pretty rare.”

The initial part of the exercise lasted about two hours and was followed by a six-hour hostage situation exercise by the Columbia Police Department. Other agencies moved to Ashland, where an active shooter drill was held at the Southern Boone County R-1 Elementary School.

In addition to testing law enforcement agencies, the exercise also prepared local media for how law enforcement would handle an active shooter incident. While reporters were allowed to go within a few dozen feet of the entrance to Laws Hall, they would be held much farther away, out of the line of sight and fire, in a real event, MU spokesman Christian Basi said. Basi said getting accurate information to the public through media in such an emergency would be important.

In the case of a shooter on the MU campus, the university would use its online MU Alert system to provide quick, accurate information. Basi and Major Brian Weimer of the MU police said they wanted to minimize the spread of rumors.

“We’ve had, in the past, traffic that has gone out and people pick it up, put it on social media, and there are rumors flying everywhere,” Basi said.

In a real event, law enforcement would be focused on stopping the shooter, Weimer said. Students, faculty and staff should expect to make decisions on their own about whether to stay where they are or go to a safer location, he said.

In addition, the university will be urging students to call their parents immediately to let them know they are safe.