The man who went on a shooting rampage that killed 10 people in Alabama told friends in the days leading up the attack that he was depressed and felt he was a failure.

Michael McLendon spoke to friends about being upset over not being able to have a career as a marine or a police officer, investigators said at a news conference late Thursday night.

Nine of McLendon's 10 victims were gunned down with bullets from a semi-automatic weapon in two rural Alabama counties near the Florida border Tuesday afternoon. The 10th victim, his mother, was weighed down on a couch in her home and set ablaze by the suspect.

Five of the victims were family members, while the remainder were relative strangers killed while he drove through town shooting from his vehicle before going to his former place of employment. After a shootout with police, McLendon died of an apparent self-inflicted gunshot wound.

Officials said McLendon had joined the marines in 1999 but was discharged a month later for fraudulent enlistment.

He had also tried to join the Samson Police Department but had been unable to complete some of the physical requirements at the state police academy, officials said.

A confidant has told investigators that McLendon felt despondent about the events. But the confidant did not believe the man would turn violent, said Jerry Conner, chief of the Alabama Bureau of Investigation.

It appears McLendon drifted between jobs after his failed efforts to have a career with security forces, Conner said. He worked at the metals factory where he died at the end of his shooting spree, before quitting a job at a sausage factory about a week before the killings.

Note found

The confidant has also told investigators that McLendon spent much of his free time at a local firing range, Conner said.

There's also evidence that suggests McLendon had been planning the attacks, said district attorney Gary McAliley.

The gunman also kept a notebook containing the names of people he had worked with and things he felt they had done wrong to him, McAliley said.

People who worked at both businesses were named in the notebook.

Authorities said they have learned more about McLendon since the shootings, but there is still no indication about what may have triggered the incident.

The information collected about McLendon so far has given investigators "a window into what happened," Conner said. "But this sort of violence and rage, it just boggles the mind.

"I don't think anybody could have anticipated this by looking at him and interacting with him," McAliley said. "But certainly he had a volcano inside of him."

Officials said a two-page, handwritten letter has also been found, in which McLendon admits to having killed his mother and indicates plans to commit suicide.

The note also mentions a family dispute over a legal issue, but doesn't contain any indications that he intended to kill other relatives, officials said.

With files from the Associated Press