Investigators trying to figure out why Steven P. Kazmierczak killed five students and wounded 16 others at Northern Illinois University last week have been frustrated by the gunman’s apparent zeal to cover his tracks.

According to today’s Chicago Tribune, Mr. Kazmierczak, an NIU alumnus and former graduate student at the University of Illinois at Urbana-Champaign, removed and disposed of the hard drive from his laptop computer and an equally important component of his cellphone. Both steps are making it much harder for the police to establish a motive behind the shootings.

Nearly a week after the attack, “we don’t have anything to know or even begin to assume a motive yet,” the university’s police chief, Donald Grady, told the Tribune.

Meanwhile, faculty and staff members are getting trained this week by counselors on how to prepare for the return of students and the resumption of classes on Monday. —Andrew Mytelka