Multi-tasking is a modern idiom dating back to the 1990s with origins in computer engineering. Seemingly, a high-powered computer can perform several tasks at once. A single-core computer performs a single task at a time, while a dual-core processor can multi-task.

In the same era, the term was applied to people. Single-core processor human beings, the theory told us, could multi-task like a computer by accomplishing two or more tasks at once with equal effectiveness and results.

There's now a strong body of evidence and research that effectively refutes this theory. Basically, human multi-tasking is a myth. Dr. Edward Hallowell is one of many researchers that covers this concept well. He wrote that multi-tasking is "mythical activity in which people believe they can perform two or more tasks simultaneously as effectively as one."

Multi-tasking while working, studying for an exam, or performing most tasks just doesn't work out.

Now, apply this to police or tactical work. Civilians who attempt to multi-task can do so in a relatively safe and sterile environment. Mistakes can often be corrected. Subpar work can be improved with a do-over. Cops, unlike the civilians we protect, have to deal with bad guys trying to kill us. All of our focus needs to be on that dimension. At an active-shooter event, the mission upon arrival is first and foremost to find and engage the shooter. Is the shooter down and no longer a threat or is he still a viable danger? Multi-tasking won't help resolve this issue.

In his book "Just 2 Seconds," Gavin de Becker addresses the problem with multi-tasking. He gives the example of a high-profile protective detail. You can't expect your protectors to be 100% effective, if you try to task them with mundane, collateral jobs such as carrying and stowing luggage or fetching coffee. The mission should be the main focus. The mission at the active shooter event is to stop the killing.

An active-shooter call usually doesn't go according to protocol. You most likely will not arrive with an optimal number of personnel for a four-officer contact team, let alone a four-officer rescue team. The site will not always be in a building with hallways and classrooms or offices like your training building.

It took some "experts" and trainers longer than others to realize that a single officer response may be what is required to stop the killing. Waiting for those additional three just doesn't work. Yes, it's dangerous. Yes, you can get badly hurt or killed. The first officer on the scene may do a walk-by triage when dealing with those down and wounded. There are critical wounds and injuries, such as arterial bleeding, which is time critical. That's going to call for a tough decision if the shooter is still active and you're short on personnel to address the problem.

The mass killing at the Sikh temple in Oak Creek, Wis., in August, occurred both inside and outside the temple. Lt. Brian Murphy of the Oak Creek PD was shot and wounded nine times in the parking lot as he tended to one of the wounded. This, my readers, is one tough and courageous cop. We really can't pay him higher praise.

Was Lt. Murphy multi-tasking at the exact time he was shot or was he the victim of bad luck? I don't know, but he certainly deserves our long-term respect for his valor.

Realize that your response to an active-shooter event is going to involve damage control. In most of these mass shootings, the first officers on the scene will be confronted with a lot of blood from the dead and dying. Our first instinct can often be to render aid. But, multi-tasking is a concept best left to computers.

Nobody said this mission was going to be easy. Stay switched on.