CHICAGO – A handwritten note threatening a Wednesday shooting at Western Illinois University prompted increased police presence on campus, while students were given the option of skipping classes without penalty, officials said.

The threat left at an apartment near the 11,000-student campus in Macomb triggered a university alert system and comes slightly more than a month after a gunman killed five students and himself at Northern Illinois University in DeKalb, just about 150 miles northeast of WIU.

“That’s the first thing that comes to your mind,” said Bonnie Barker, WIU spokesperson. “You don’t want that here.”

An employee at an off-campus apartment complex received the note that was left in a drop-box sometime late Tuesday or early Wednesday, university officials said.

“Basically, the letter said there would be a shooting on campus today,” said Robert Fitzgerald, the head of WIU’s office of public safety. He declined to provide details about the note, including its exact contents.

No suspect was in custody, Macomb police said.

WIU officials told students they could choose not to attend Wednesday classes but stopped short of canceling them or imposing a full lockdown.

Patrick Schultz, senior at WIU, lives on campus and said he woke this morning to the ringing of his room phone with an emergency message about the note.

Introduced last year after a shooting at Virginia Tech University that left 32 people dead, the university’s alert system includes automatic alerts by cell phone text message and e-mail. The university activated the alert system at around 9:30 a.m. Wednesday, shortly after the note was found, Barker said.

“While this is an anonymous off-campus threat, it is imperative that we take all necessary precautions to ensure the safety of our students, staff and faculty,” said Al Goldfarb, president of WIU.

Pamela Nisivaco and Brittany Abeijon contributed to this report