A credible threat possibly linked to the 20th anniversary of the Columbine shooting brought a whirlwind of chaos to schools in the metro area yesterday, April 16, including a district-wide lockout in Denver.

Now, Denver Public Schools says it's reviewing its lockout procedure, which prompted confusion yesterday.

"It's not very often that an entire metro area gets an alert like this," says Anna Alejo, the district's chief communications officer, noting that the district's chief of safety called an all-district lockout "unprecedented."

On Tuesday, law enforcement were made aware of a credible threat to schools from Sol Pais, an eighteen-year-old woman considered armed and dangerous who had traveled to Colorado from Florida. According to law enforcement, Pais is "infatuated" with the Columbine shooting and its perpetrators and purchased a shotgun and ammunition when she arrived in Colorado.

Alejo says that starting at 1:15 p.m., the district was working with law enforcement on a lockout at Grant Ranch, a K-8 school in Littleton, because authorities were searching for Pais in that area. Around 3 p.m., DPS became aware of the need for lockouts across the district after seeing a tweet from the Colorado Department of Education:

Due to a credible threat to schools by an individual identified by the FBI, the Department of Public Safety recommends all schools in the Denver metro area conduct a lockout and controlled release immediately. More info to come. #edcolo — CO Dept of Education (@codepted) April 16, 2019

Lockouts are different from lockdowns in that normal school activities still happen inside the building, but no one can enter or exit.

But by the afternoon, students were already on athletic fields at schools around the district, getting ready for games or warming up for practice. Around 3:35 p.m., a South High School staff member heading toward the school parking lot told us she hadn't received any security instructions from her administrative staff, but had heard about the threat from the media.

Alejo says the district sent texts and other alerts to all parents at 3:50 p.m. advising them about the lockouts. However, some parents hadn't received any notifications by around 5:30 p.m. Westword's culture editor received an email around 5:15 p.m. that his son's DPS after-school care program, which starts at 3:45, had been canceled. Around 5:35 he got a call from the program notifying him that it hadn't been canceled but that he should still pick up his son immediately.

Sol Pais is considered armed and dangerous. Jefferson County Sheriff's Office

Alejo says that DPS alerted all district staffers before 4 p.m. that they should "bring the students who were out on fields inside" and that it reached out to all school leaders around 4:05.

But not everyone got that message.

"This, from a school district perspective, is the worst time of day for something like this to happen because we have students already out on the fields, and coaches aren't necessarily looking at their messages," says Alejo. "It most definitely creates confusion."

That may explain why student athletes at South were walking toward school from the athletic facilities around 4:15 p.m., close to an hour and a half after the Department of Education's tweet. Students said they were told they should go home if they had rides or wait inside until someone could pick them up.

Around the same time, the district tweeted about the lockouts. But some parents wanted to know why the tweet was coming only then.

What took so long? I drove by my kids school and the after school activities were all outside. Why did it take an hour for DPS to formulate a plan and an announcement? — Mr Army Retired (@LivingTheDrea__) April 16, 2019

"We'll definitely be doing an after-action review to see what we can do to do a better job next time," says Alejo.

A joint law enforcement investigation involving the FBI and Colorado Department of Public Safety and being led by the Jefferson County Sheriff's Office is currently under way regarding Pais. Anyone with information about her whereabouts is asked to contact the FBI tip line at 303-630-6227 or email denverfbitips@fbi.gov.