RALEIGH, N.C. (AP) _ A student who left a noose hanging from a tree at Duke University has been disciplined but can return to campus next semester and won’t face criminal charges, the university said Friday.

In announcing that it finished its investigation, the university also released an open apology letter written by the person responsible, who says the noose was made as a joke and carelessly left behind. The discovery of the noose last month sparked outrage on the school’s Durham campus and made headlines across the country.

The letter says the person didn’t fully understand its historical connection to lynchings in the South.

“Once I realized the historical connotations, I contacted the Administration, and explained that I never had any racist intent _ which anyone who knows me could testify to,” the letter states. “I apologized and co-operated in every which way I could.”

The university said its investigation determined the noose was left as a result of ignorance and bad judgment. Investigations by law enforcement officials have also concluded.

The undergraduate student, who hasn’t been identified, said the noose was part of a poorly conceived joke.

“My purpose in hanging the noose was merely to take some pictures with my friends together with the noose, and then texting it to some others inviting them to come and `hang out’ with us _ because it was such a nice day outside. If there was ever a pun with unintended consequences _ this was certainly one,” the letter says.

Officials say the noose was found about 2 a.m. April 1 in the plaza outside the Bryan Center, the student commons building. Black Student Alliance Vice President Henry Washington has said he and about 14 other students saw the noose hanging overnight after being alerted via Twitter.

Washington said he’d be releasing a statement later Friday.

The afternoon after the noose was found, thousands of students and members of the Duke community gathered in front of the university’s Gothic chapel building. Duke President Richard Brodhead told the crowd that their presence was a rejection of what nooses symbolize in a region where lynchings were once used to terrorize black residents.

The next day the university announced that the person responsible had admitted to leaving the noose hanging in the tree and had left campus as the school started discipline proceedings that could include expulsion.

University spokesman Michael Schoenfeld declined Friday to elaborate on how the student was disciplined or whether the person’s absence from campus was voluntary or part of a suspension. The university has declined to describe the student’s gender or race, citing privacy laws.