While active-shooter training is not new to houses of worship, the massacre this month at a Texas church has renewed attention to their vulnerability and the fine line religious leaders walk as they try to create a welcoming atmosphere that doesn't tempt a would-be shooter.
"One of the responsibilities I have as a pastor, as a shepherd of the church, is to protect the people, and that includes spiritually, but it also includes the physical protection," said Pastor Jack Graham of Prestonwood Baptist Church in Plano, Texas.
The deadliest-ever mass shooting in Texas -- in which a gunman walked among pews at First Baptist Church in Sutherland Springs, killing 25 parishioners and an unborn child -- has become the latest in a string of attacks directed at religious institutions.
Now, Christian leaders, in particular, are considering new security measures or bolstering existing rules, mirroring actions taken by leaders of Jewish, Muslim and other faith communities when their institutions have been targets.
"We need to be doing everything we can right now to protect our people," Graham said, "and that includes visible police officers, volunteers and keeping our eyes open."
At a congregation in central Florida, volunteers who welcome parishioners every weekend know they also need to remain alert.
"The more you understand what is normal, the easier it is to spot what is abnormal," said Eric Little, associate pastor of Bethel Baptist Church in Lakeland.
The church has installed security cameras, and doors remain locked during services. The minister said it was an adjustment for many but "people feel safer and they understand why."
"The church should be a safe place," Little said. "We are hoping we are doing that. People are welcome. We are not trying to keep people away."
For Pastor Darius Pridgen of True Bethel Baptist Church, preparedness has become a priority.
Volunteer security guards patrol the Buffalo, New York church, and on Sunday, parishioners are due to learn "run, hide and fight back" techniques from local police.
People need to know where exits are and how to pay attention if a threat emerges amid the music, prayers and solemnity, Pridgen said.
"It doesn't give me any pause; it's the world we are in," he said, pointing out that no one used to worry about so-called soft targets, such as movie theaters and churches.
At some places of worship in Texas, ushers and greeters serve double duty as armed guards.
Chuck Chadwick, who founded the National Organization of Church Security and Safety Management, has trained more than 350 parishioners and pastors to become certified security officers approved by the Texas Department of Public Safety.
During a six-day training, Chadwick teaches volunteers handgun skills, de-escalation techniques, and hand-to-hand tactics, such as handcuffing suspects.
"You could think of them as bodyguards," Chadwick said.
Until recently, churches in Texas were required to hire certified officers as armed security.
A state law that went in effect in September now allows churches, synagogues and other places of religious worship to create their own security teams with volunteers who are legally allowed to carry guns.
"I would rather arm law-abiding citizens and make sure they can prevent this from happening, as opposed to trying to pass laws that would prevent law-abiding citizens from having guns," Texas Attorney General Ken Paxton told Fox News Channel.
At least five volunteers trained as guards are on duty every Sunday at Trinity Lighthouse Church in Denison, Texas.
Pastor Brian Ulch said his team opted not to hire a private security firm because "they don't know your congregation; they don't know the heartbeat of your ministry."
Ulch says the 750-member church nestled in the northeast Texas Hill Country, 75 miles outside of Dallas, is prepared for a shooting scenario, as well as other dangers.
Those include "the hot topics that pastoral teams touch every day that can be controversial that can lead to picket lines, to protests," he said. "You never know what you're going to engage on a Sunday-to-Sunday basis, and doing nothing was not an option."