Madison police spokesman Joel DeSpain said the 19-year-old resident, who had friends sleeping over, was first made aware of the 18-year-old intruder on the night of Oct. 9 when he opened his bedroom door and turned on the lights, The (Madison) Capital Times reported Tuesday.
"He then heard the man go to the bathroom and leave the apartment a few minutes later," DeSpain said.
The resident and his friends awoke the next morning to find a revolting mess in the bathroom, police said. The resident told police the mess took two hours to clean.
Investigators said the 18-year-old left behind his socks, pants, identification and cellphone. He was contacted by officers and advised "it would be very adult of him to apologize to the people in the apartment," DeSpain said.
The apartment residents declined to press trespassing charges.