BOULDER, Colo. (KDVR) – A man was arrested in Boulder, Colorado, Tuesday morning in connection with threats made against the University of California, Los Angeles.

Boulder Police Chief Maris Herold said the department was notified of an 800-page manifesto written by the suspect, 31-year-old Matthew Christopher Harris, Monday night.

Harris’ writings were first discovered after he emailed them, along with a video he made referencing a mass shooting, to members of the UCLA philosophy department, the Los Angeles Times reports. The school moved all classes to remote instruction Tuesday out of an abundance of caution.

In the manifesto, the former philosophy postdoctoral researcher allegedly made thousands of references to violence including specific comments about Boulder. Because of this, Boulder PD was notified.

The department was able to find his address and Tuesday morning began evacuating schools, homes and businesses in the area around 8 a.m. A total of 65 homes were ordered to shelter in place.

“I recognize that today was a scary day for the people of Boulder,” District Attorney Michael Dougherty said.

Boulder crisis negotiators were able to contact Harris during the morning. Just after 11 a.m. he came out of his apartment peacefully and was taken into custody.

“The importance of having collaboration at the federal, state and local levels was critical to the swift resolution of the incident this morning,” Herold said during a news conference Tuesday afternoon.

While it’s not clear if this is connected to the threats, Herold said Harris attempted to purchase a gun in November, but was denied due to a protection order out of California that prevented him from owning guns.