Police are still working to determine the motive behind this senseless tragedy.

From the New York Times:

Police, Still Seeking Motive, Find Note in Delta State University Murder-Suicide

The day after thousands of people gathered for a candlelight vigil memorializing a professor killed by a colleague, investigators continue to search for a motive.

The police believe that Ethan A. Schmidt, an assistant professor at Delta State University, was shot on Monday by Shannon S. Lamb, who taught geography and social science at the college. Dr. Lamb is also suspected of fatally shooting his girlfriend and, later that day, himself, the police said.

“I am so very sorry,” he wrote in a note after apparently shooting Amy Prentiss, 41, at the home they shared in Gautier, Miss. “I wish I could take it back.”

He also called 911 shortly after 10 a.m. Monday, telling a dispatcher that he had shot his “wife.”

“There’s a dog in the house and he’s a sweet dog, not going to bother anybody, but I’m sure he’s upset,” Dr. Lamb can be heard saying in the recording.

He declined to give his name before hanging up.