Derrick Todd Lee died five days after he was transported from the Louisiana State Penitentiary in Angola for emergency care, state prison officials said. An autopsy will be performed.
Lee, 47, was on death row for the 2002 murder of Charlotte Murray Pace, 22, and had a second-degree murder conviction for the death of Louisiana State University graduate student Geralyn DeSoto, 21, who also died in 2002.
He was linked to the deaths of five other women, but was not tried in those cases. An eighth woman survived.
Ann Pace, mother of Charlotte Pace, told CNN Baton Rouge affiliate WAFB
that Lee "had an unwanted seat at the table. You don't want him there. But he has a seat at the table in your head."
While observers spoke of at least some closure for relatives of victims, they also cited the nature of the crimes.
"I don't think it will ever end for the victims," Tony Clayton, who prosecuted Lee in the DeSoto killing, told WAFB. "They are always going to have it deeply embedded in their mind how their loved ones were brutally murdered."
Clayton also spoke of Lee's behavior in the years since the crimes.
"A lot of time serial killers they deny all the way to the end and that is what Derrick did, even when we had him red-handed with DNA."
The state Department of Public Safety and Corrections said it could not comment on Lee's medical condition because of privacy laws.
Former Baton Rouge Police Chief Pat Englade recalled long hours put in by members of a task force investigating the killings and trying to put an end to them.
"This is one of the most traumatic things that's ever happened in this city and I think that today we can look at it and say justice was done," he told CNN affiliate WBRZ. "Somehow, I think Derrick Todd Lee needed to die for what he did to these people."