The bananas were scrawled with the letters “AKA Free.”
AKA, or Alpha Kappa Alpha, is a predominately African-American sorority.
The university, in Washington DC, recently swore in its first AKA sorority member and its first female African-American student government president.
“I regret this happened, apologize to everyone offended, and state emphatically that this incident does not reflect what American University truly is,” university President Neil Kerwin said in a statement.
The university set up several meetings for students to discuss the incident. It also released surveillance video of the suspect from the Monday incident and is offering a $1,000 reward.
The AKA says it is worried about its members on campus.
“We … urge American University to strengthen the security measures on campus to keep its SGA President, who also is an Alpha Kappa Alpha Sorority member, other Alpha Kappa Alpha Sorority members and African Americans on campus safe,” it said.