Officials confirmed Cotton Creek Elementary entered lockout during the response.
All high schools in the Roaring Fork School District were closed Thursday and others were in lockout due to an anonymous tip.
The school went on lockout at around 3:22 p.m., according to Denver Public Schools, which reported the lockout Wed.
Two Adams County school are on lockout due to nearby police activity.
The lockout at four schools was lifted Tuesday after an armed robber escaped a police perimeter.
The lockout has been lifted at Thornton High School and the Bollman Technical Education Center, police said.
Police found no injuries, but did locate shell casings in the area.
The victim of a Friday morning shooting at a North Boulder mobile home park identified.