Churches are traditionally places we think of as not only being sacred, but safe. But that image was shattered after the mass shootings in South Carolina and Texas.

The threat of violence presents a unique challenge for institutions like churches. Unlike schools, hospitals and courthouses, churches are constrained when it comes to subjecting visitors to security measures. That leaves church leaders concerned they may not be doing enough, so they want to know all they can about providing security. 

At the nation's largest insurer of church buildings, Church Mutual Insurance Company, the number of customer calls continues to rise. Church Mutual's Vice President of Risk Management Cheryl Kryshak said churches by nature want to be open and welcoming, but they also have to protect those inside from threats. Kryshak said she hears two primary concerns from religious leaders: first, securing the church's perimeter, which involves locks, lights and surveillance cameras. The second is concern about someone inside the sanctuary behaving strangely or threateningly.

Ushers are the first line of defense, Kryshak said, and they have to be trained to be more than greeters. They must be able to observe who is entering the church, and they should speak with whomever they don't know to gauge their state of mind. Also, in the case of an emergency, parishioners must know how to react. An emergency evacuation plan is essential, Kryshak said.

Though the insurer doesn't take a position on arming church staff, the company does say if a church decides to do so, guns should only be used by those trained to use them — like police officers or military personnel.

In Boston, church leaders have been meeting to share ideas about providing security that is effective, but not intrusive. Nancy Taylor, senior minister of the historic Old South Church on Boylston Street, acknowledges that security measures can be an additional burden, especially when it comes to cost. But she says they must be implemented.

Still, the church's mission is to be a welcoming place of refuge. And those who do enter, do so through a carefully-monitored corridor equipped with cameras. There's also a button for the receptionist to use to call 9-1-1, if necessary.  

Taylor agrees ushers are the key to protecting the congregation, and her advice to them is to be welcoming and watchful. After the shootings in Texas and South Carolina, Taylor sent a letter to the ushers at her church, thanking them for what they do and reminding them how important they are to keeping the church safe.

On Tremont Street across from Boston Common is the Cathedral Church of St. Paul, which has an sandwich board outside that welcomes visitors. It's a welcome that also comes with a warning: "No violence and threats of violence, even if you are in the right."  Explaining the sign, Acting Dean Nancy Gossling said, "we welcome all people, but we don't welcome all behaviors."

It is a new reality church leaders must face: walking that fine line between security and openness — keeping their doors, and their eyes, open.