Authorities announced Wednesday that they know who killed a University of Missouri professor in a campus parking garage eight years ago, but that they may never be able to explain the vicious attack because the suspect committed suicide last summer.

Campus police said at a hastily arranged news conference that two people recently implicated Timothy Aaron Hoag in the Aug. 9, 2012, stabbing death of 72-year-old Jeong Hyok Im, whose body was stuffed into the trunk of his car, which was then set on fire. Blood, hair and DNA evidence collected at the crime scene has been matched to Hoag, said campus police Chief Jack Watring.

In August, Hoag jumped to his death from the roof of a different parking garage without leaving a suicide note behind. He was 35 years old. Those who implicated Hoag said they did so only after he died because they were afraid he might harm them, Watring said. Hoag's criminal record includes assault and drug convictions.

"We never stopped working on the case, examining every lead that came to us, day and night, for a long eight years," Watring said.

University police Capt. Brian Weimer said Hoag apparently didn't know Im and investigators don't know why he killed him. Im's death sent a wave of fear through the city, particularly through its close-knit Korean-American community, of which Im was a part. Im earned a doctorate from the University of North Carolina-Chapel Hill after emigrating to the United States four decades ago and worked at several universities, including Harvard, before he joined the Missouri faculty in 1987.

"This loss was a very, very traumatic one for our university," said Chancellor Brady Deaton. "Our hearts were broken for the Im family. ... It's haunted us for the past eight years."

Watring did not disclose the names of those who implicated Hoag. He said investigators believe Hoag acted alone and that they don't consider either of the witnesses to be accomplices in Im's killing.

The chief said one of the two came forward in late December with information linking Hoag to the crime. He said the second person later told police he drove Hoag to the garage that day and returned two hours later — parking a level below where the attack happened — with a gasoline can Hoag had asked for. He said Hoag came to get the gas and left, then returned later wearing a painter's mask and hooded sweatshirt that covered his head — a description that matched the killer.

Watring said detectives believe the witness' claim that he or she didn't know what Hoag had been doing at the garage.

"(Hoag) was the only one who knew about this," Watring said.

Hoag apparently didn't know Im, university police Capt. Brian Weimer said. Im's slaying doesn't appear to have factored into Hoag's suicide, but Hoag didn't leave a note behind. He said Hoag was injured in a car accident not long before his death, and that may have contributed to his suicide.

Online court records show that Hoag pleaded guilty to misdemeanor assault and tampering with a victim or witness in March 2001 in Boone County, serving six months in jail. He spent another five days in jail in March 2005 after being convicted of a misdemeanor drug paraphernalia charge.

In a statement issued through the university, Im's family thanked campus police for their "tireless commitment" to the case and said Wednesday's announcement will help bring closure to the case.


Alan Scher Zagier can be reached at http://twitter.com/azagier