Plan for the worst-case scenarios, and train for them on a departmental level. It may be a major task to coordinate, and it will be costly and time-consuming. However, training is the only safe place to try out the elements of your proposed plan and make corrections. Training is the time when mistakes can be made without sacrificing lives. Without a planned, coordinated response, which has been practiced and perfected, the lives of everyone on scene will be at unnecessary risk. Approaching an active criminal sniper cold is inviting catastrophe.
Take special care to properly prepare your patrol personnel. In all sniper incidents, they will be among the first to make contact with the shooter. They will often be counted among the first casualties. They need to know the potential threat they will be facing, and how to respond to safely contain the shooter. They also need to be equipped with weaponry that will give them an equal chance in fighting the sniper. Handguns and shotguns are no match for a barricaded sniper with a scoped rifle. But upgraded equipment is useless without upgraded training to match.
Develop a structured operational sequence for locating, isolating, and neutralizing the sniper as quickly as possible. This plan will be put into motion by the first responders, but as the incident goes on, it will have to be continued by arriving SWAT personnel. Classroom instruction, provided by qualified and knowledgeable personnel, is the best starting point for this process. Practical exercises help to fine-tune the plan and reinforce the details.
A criminal sniper incident is like nothing else in police work. Safely resolving it requires planning and training. Realizing the probability of such an incident taking place in your jurisdiction, and not taking immediate action to prepare your personnel to handle it, borders on deliberate indifference. The chief of the Austin (TX) Police Department at the time, Robert Miles, gave a news conference shortly after the Texas Tower shootings. He sounded almost prophetic when he said, "This could have happened in any city in America, or in the world for that matter."
For the last 50 years, he has been right. The question you have to ask yourself and your agency is, "Are you ready for the next Charles Whitman?"