SAMSON, Alabama (CNN) -- The man who killed 10 people, then himself, in a shooting rampage in southern Alabama had failed in his dreams both to become a U.S. Marine and a police officer, and was depressed and unhappy with his life, investigators said Thursday.
The shooter, Michael McLendon, killed his mother before killing others.
Michael McLendon, 28, fatally shot his mother in his hometown of Kinston on Tuesday before driving to nearby Samson and Geneva, killing nine more, then fatally shooting himself after a shootout with police.
Authorities are calling it the deadliest single assault in recorded Alabama history.
"He was going to go until he was stopped, by himself or someone else," said Col. Chris Murphy of the Alabama Department of Public Safety.
"He had obviously planned to go out in grand style."
McLendon left behind a letter, apparently after killing his mother, that described how he did so and saying that he planned to kill himself, according to Murphy. The letter "describes how McLendon harbored ill feelings toward family members due to a family dispute."
McLendon -- a self-proclaimed survivalist who was known to train with the rifles he used in the shooting spree -- enlisted in the Marines in 1999, but was kicked out one month later for "fraudulent enlistment," Murphy said.
He was hired as a police officer in 2003, but let go a month later for what Murphy called physical issues.
The nearly hourlong assault ended 24 miles from where it began at Reliable Metal Products plant in Geneva, where McLendon had worked in 2003.
"McLendon made statements of being depressed and was dissatisfied with his present position in life," Murphy said. "His dream was to become a Marine, and later a police officer. Both those dreams were unfulfilled."
McLendon was armed with two assault rifles -- an SKS and a Bushmaster -- and two pistols, and a shotgun was found in his car.
"At this time, we believe that he fired in excess of 200 rounds during the assaults," the Department of Public Safety said in a news release.
McLendon had no known criminal record before carrying out the rampage, officials said.
Coffee County district attorney Gary McAliley said neighbors and co-workers described McLendon as quiet and shy. Some neighbors complained that he was always shooting firearms behind his home, he said -- but feared only that McLendon would accidentally kill one of their cows. Watch how the shaken towns are trying to cope »
Co-workers at Kelley Foods, where he unexpectedly resigned last week, said they had a nickname for him -- Doughboy -- that he didn't like.
"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."
McLendon called the Samson City Hall about 1 p.m. Tuesday and asked whether the city council would be meeting in the evening, Michelle Flanery, magistrate and billing clerk, told CNN Radio. Flanery said she replied that there was no meeting scheduled that day and that McLendon thanked her before hanging up.
Authorities said McLendon also had a list of current and former co-workers, some whose names were accompanied by notes on ways he felt they'd wronged him. But the note was not a "hit list," as had been reported, and none of the people whose names were listed were attacked, they said. View images from the rampage »
Among the dead were the wife and toddler of Geneva County Sheriff's Deputy Josh Myers, who was involved in the standoff with McLendon before he realized his own loss.
His 3-month-old daughter, Ella, was also wounded. She was rescued by a neighbor and released from a hospital in Pensacola, Florida, Thursday evening.
The shootings rattled Samson and Geneva, neither of which has a population beyond 4,500 people, and sent shock waves outside the small towns affected.
"This event formed the single deadliest crime recorded in Alabama," said Murphy of the Department of Public Safety.
Alabama Gov. Bob Riley arrived in Geneva County on Wednesday afternoon, pledging support to the community and members of law enforcement.
"I think it's a combination of just shock and disbelief," said Riley, a native of Ashland, Alabama, population 2,500, in east Alabama. "I live in a little small town about like this, and I know what it would be like in my community. It really is devastating to a community this size." Watch the governor respond to the rampage »
"This doesn't happen in small towns, and all of a sudden you begin to understand that you really do have the same problems in some of these small towns you have in other parts of the country."