Last Updated Sep 16, 2015 4:30 PM EDT
GAUTIER, Miss. -- Shannon Lamb's motive for fatally shooting his girlfriend and a university colleague remains largely a mystery: The university instructor had no criminal record, he was a well-liked teacher, and police said there was no history of domestic violence between him and Amy Prentiss.
And yet there were some signs of trouble: Cleveland Police Chief Charles "Buster" Bingham said Tuesday that authorities had some indication Lamb and the second shooting victim, Delta State University professor Ethan Schmidt, did not get along.
A student who praised Lamb, Brandon Beavers, said the professor also seemed agitated and jittery, "like there was something wrong with him." And another student, Mikel Sykes, said Lamb told him he was dealing with stress at the end of the 2014-15 academic year.
Lamb also had asked the university for a medical leave of absence, saying he had a health issue of some sort, university President William LaForge has said.
This year, he was only teaching two online classes, and recent changes in the university's hiring policies meant the doctorate Lamb had worked so hard to earn would not guarantee him an automatic tenure track.
Nonetheless, authorities have not been able to identify any one major factor that would have driven Lamb to shoot two people and then kill himself.
In a 911 call Monday, Lamb told police he had shot Prentiss and that officers needed to get over to their house. Lamb made a point to say his "sweet dog" was there alive and probably upset, and said the dead woman's family contacts could be found on her phone.
Inside the home, officers found Prentiss' body and a handwritten note in which Lamb described her as "the only woman who ever loved me" and wrote "I wish I could take it back."
News of the shootings of Prentiss in Gautier, Mississippi, and of Schmidt at Delta State, 300 miles away, shocked many.
"We're talking about a guy who was highly dedicated to his children and to his students," a former student of Lamb's, Hannah Rapetti, said of him. She said Lamb spoke lovingly of Prentiss, was a dedicated father to his two children, and a devoted teacher who helped her find a scholarship so she could stay in school.
"Without him I wouldn't have made it through college," Rapetti said.
Police in Gautier said Lamb had no history of violence or criminal record. Schmidt himself had included Lamb in a book he wrote where he acknowledged the "wonderful people" he shared his academic life with.
Bingham said Tuesday that authorities had some indication Lamb and Schmidt did not get along at work. And he said Lamb had told some people that he had a spider bite on his face, which sparked the request for medical leave.
"We've got a lot of questions. We don't have answers yet. You could write this off to a disgruntled employee. There's obviously something there that brought this about," Bingham said.
After fleeing the campus, police later picked up Lamb's trail when he crossed back into Mississippi from Arkansas. Before he could be apprehended, Lamb killed himself with a single .38-caliber handgun in the backyard of a home about a mile south of his parents' home on the outskirts of Greenville, Mississippi, said Washington County Coroner Methel Johnson.
His car was still running in the driveway. It was not immediately clear why Lamb went to that home, though Johnson said she believes he knew the people who lived there. Lamb grew up in the area.
Lamb started working at the university, which has 3,500 students in a city of about 12,000, in 2009 and taught geography and education classes. He received a doctorate in education in the spring.
Lamb and Prentiss had apparently been dating for some time. In the 911 call, Lamb said "I killed my wife," but there was no record of them ever marrying. They had a dog named Lightning that lived with them at the brick house that backs up to a bayou in Gautier. Police said the dog was OK.
Prentiss' ex-husband, Shawn O'Steen, said they divorced 15 years ago but remained friends and had a daughter who's now 19.
"She was completely devastated," O'Steen said of his daughter. "She and her mother were absolutely best friends."
O'Steen said he had not met Lamb but heard through his daughter Abigail that Lamb was interested in music and played the blues. Lamb met Prentiss when he and Abigail both performed at a summer fair three years ago. Prentiss was a nurse who worked for various companies online.
Mike Shaffer, who works at The Julep Room, a bar near Gautier, said he last saw Lamb and Prentiss the night of Sept. 5, after Lamb had finished playing his guitar and harmonica. There was no sign of anything amiss.
"Just a happy couple. We were cutting up and throwing one-liners at each other," he said.
Schmidt, the slain professor, directed the first-year seminar program and specialized in Native American and colonial history, said Don Allan Mitchell, an English professor at the school. He was married and had three young children.
He studied at Emporia State University in Kansas and was president of his fraternity and student government.
After a vigil Tuesday night at the university, classes were to resume Wednesday.
"We're trying to get our students to come back," LaForge said. "The crisis is over. This is a day of healing."