DeKalb, Ill. Steven Kazmierczak had the look of a boyish graduate student - except for the disturbing tattoos that covered his arms.
Professors and students knew him as a bright, helpful scholar, but his past included a stint in a mental health center.
Many saw him as happy and stable, but he had developed a recent interest in guns and was involved in a troubled - possibly abusive - on-again, off-again relationship.
What people initially told police about the Northern Illinois University shooter didn't add up, and now investigators are searching for answers to what triggered Thursday's bloody attack, in which five students were killed and several more injured before Kazmierczak committed suicide.
While searching for a motive, authorities questioned family and friends and tried to determine whether he had recently broken up with his longtime girlfriend.
One person who knew the couple, who spoke to The Associated Press on the condition of anonymity, said the couple's relationship was on-again, off-again and "really rocky." Kazmierczak was controlling, she said.
"He was abusive, had a temper," she said. "He didn't actually hit her; he would push her around."
The 27-year-old Kazmierczak also had a history of mental illness and had become erratic in the past two weeks after he stopped taking his medication, said university Police Chief Donald Grady.
A former employee at a Chicago psychiatric treatment center said Kazmierczak had been placed there after high school by his parents. He used to cut himself and had resisted taking his medications, she said.
Kazmierczak spent more than a year at the Thresholds-Mary Hill House in the late 1990s, former house manager Louise Gbadamashi told the AP. His parents placed him there after high school because he had become "unruly" at home, she said.
Gbadamashi couldn't remember any instances of him being violent, she said.
"He never wanted to identify with being mentally ill," she said. "That was part of the problem."
Jason Dunavan, a tattoo artist in Champaign, said he spent hours as recently as last month creating tattoos for Kazmierczak. His work included an image of the macabre doll from the horror movie "Saw" riding a tricycle through a pool of blood with images of several bleeding cuts in the background.
On Friday, police went through belongings Kazmierczak left at a DeKalb motel in search of clues.
Authorities found a duffel bag, with the zippers glued shut, that Kazmierczak had left in the room, said Lt. Gary Spangler of the DeKalb Police Department.
He would not comment on what was found in the bag. The Chicago Tribune, citing law enforcement sources, reported that investigators found ammunition inside.