Columbine - Denver-area schools were closed on Wednesday as authorities searched for a woman they said was a "credible threat" to the community, a scare that comes just days before the 20th anniversary of one of the country's deadliest school shootings at Columbine High School.
While she made no specific threat against schools, Mr Phillips said her comments made her a danger.
Police identified the suspect as 18-year-old Sol Pais, whom they said travelled to Colorado from Miami and threatened the schools.
A "BOLO" sent out by Rocky Mountain Safe Streets Task Force says "NO PC TO ARREST" meaning authorities at the time the BOLO was created did not have enough probable cause to arrest her.
Earlier, an Federal Bureau of Investigation bulletin said authorities lacked probable cause for a formal arrest but that law enforcement should detain Pais for a "mental health" evaluation. They say she was last seen in the foothills west of Denver, where some of the schools put on lockdown are located.
They said she should not be approached but did not provide further details about the nature of the threat except that she was believed to be in the Denver-Littleton area and "attempting to buy firearms".
All after-school activities, including sports and practices, will go on as scheduled, except at Columbine, where they were canceled as a precaution, the district said.
Gov. Jared Polis says the threat that prompted a lockdown at Columbine High School and other Denver-area schools involved someone who was armed and "may be interested in harming our schools or our kids". The students walked to crosswalks and buses parked near the entrance. The FBI is leading the investigation in Jefferson County, Fulton said.
After the threat was made public, all Jefferson County schools were placed on lockout status.
The lockdowns come just days before the 20th anniversary of a mass shooting at the school that killed 12 students and a teacher.
Earlier Tuesday, the Jefferson County Sheriff's Office issued a warning, calling the woman they identified as Sol Pais, 18 of Florida, as "extremely unsafe".
She then bought a pump-action shotgun "immediately" upon arriving in Colorado.
Almost 20 years ago, two students, Dylan Klebold, 17, and Eric Harris, 18, killed 12 students and one teacher in a mass shooting at Columbine.
School security chief John McDonald talks with judicial specialist Maryann Peratt in Columbine High Schools new library, which was built after the 1999 attack.
Junior David Eaton told the newspaper that he was in a math class when the school announced the lockout.
In a lockout, exterior doors are locked, and school continues as normal. "Children are safe. Deputies are at the schools".
The 20-year anniversary of the shooting is on Saturday. There was no immediate indication whether Tuesday's lockdown has any connection to the anniversary.