Authorities arrested a 28-year-old criminal justice graduate student in the mysterious murders of four University of Idaho students that shook a small community that hadn’t reported a murder in five years. 

Bryan Kohberger, a doctoral student at nearby Washington State University, was arrested in eastern Pennsylvania. The students – Ethan Chapin, 20, Madison Mogen, 21, Kaylee Goncalves, 21, and Xana Kernodle, 20 – were stabbed to death at a rental home near campus in Moscow, Idaho.

Court documents released days after Kohberger’s arrest detail an exhaustive investigative effort by police to locate a suspect in the case, from DNA samples, surveillance footage, cell phone tracking software, and rifling through trash at his family’s home in Pennsylvania. 

Here’s what we know about Kohberger’s past and the timeline of the investigation.

Suspect moved to Washington state months before murder

Kohberger received an associate’s degree in psychology from Northampton Community College in Pennsylvania in 2018, the school confirmed to USA TODAY. Kohberger also attended DeSales University in Allentown, Pennsylvania, where he received his bachelor’s degree in 2020 and completed graduate studies in June, the university said in a statement Friday.

He graduated with a master of arts in criminal justice, according to the school’s online commencement program. “As a Catholic, Salesian community, we are devastated by this senseless tragedy,” DeSales University said in a statement.

He then began his program at Washington State University.

WHAT WE WE KNOW ABOUT BRYAN KOHBERGER:Suspect arrested in the slaying of 4 University of Idaho students