An eye witness saw Mijailovic stab the 21-year-old inmate in the stomach with a screwdriver, totally unprovoked, he told the Aftonbladet newspaper.
The stabbing reportedly occurred at the therapy ward for the mentally ill, when the inmates were waiting to get frisked.
Both guards and inmates intervened and interrupted the attack, the newspaper reported.
Mijailovic has now been placed in an isolation cell and police have initiated a preliminary investigation for aggravated assault.
On Thursday they questioned witnesses, but Mijailovic himself won’t be questioned until after the holidays.
The 21-year-old victim of his attack was taken to hospital with injuries to his liver, but his condition is reported to be stable.
Mijailovic is now 33-years-old, and was sentenced to life in prison in December of 2004 for stabbing Lindh while she was shopping at the NK department store in central Stockholm.
While Lindh survived the initial attack, doctors were unable to stop the bleeding caused by the injuries and she died early the next morning.
Since the killing, Mijailovic has committed several violence crimes while in prison.
In 2005, he assaulted a fellow inmate at the forensic psychiatry clinic in Sundsvall in northern Sweden.
The warden at Kumla does not want to reveal any names of the people involved in the latest attack, but he confirms that Mijailovic has been violent in the past.
“It is fairly well known that Mijailovic is the kind of person who’s been involved in similar incidents,” Kenneth Gustafsson told Aftonbladet.
Mijailovic has previously stated that he acted mentally ill during his trials to escape a prison sentence.
“I was rambling to get forensic psychiatric care,” he said this autumn.
“Everything was made up. I didn’t hear voices.”