The man suspected of shooting dead his girlfriend, before killing a colleague at a Mississippi university, had left a note apologising, say police.
Shannon Lamb's handwritten note said: "I am so sorry I wish I could take it back. I loved Amy and she is the only person who ever loved me."
Mr Lamb, who later killed himself, is accused of murdering Amy Prentiss at her home in Gautier on Monday.
Police said he drove 300 miles to Delta State University and killed again.
Tributes have been paid to the second victim, Ethan Schmidt, a history teacher at the university in the city of Cleveland.
Police in Gautier said Lamb called them at 10am local time on Monday and said he had shot and killed someone, but without any explanation.
When police got to Ms Prentiss's home they found the note and the 41-year-old woman's body.
But there was no hint at the horror Lamb was about to unleash at the other end of Mississippi.
A few hours later, shots were fired at the university, which is a five-hour drive away, and the campus was put on lockdown.
Ethan Schmidt, a history teacher, was found dead in his office from gunshot wounds.
A brief manhunt followed the university shooting but Lamb told police on the phone that he was "not going to jail".
Police located his car but after he pulled over, he jumped out of the vehicle and shot himself.
A longtime friend of Lamb, Carla Hairston, said the college professor was smart, charismatic and funny.
Police say they were still searching for a motive in both killings.
Detective Matt Hoggatt, one of the investigating officers, said there was no indication that drugs, alcohol or domestic violence played a part and there is no suggestion that Mr Schmidt and Ms Prentiss had a romantic relationship.