BOSTON (AP) — Tests conducted on the brain of former football star Aaron Hernandez showed severe signs of the degenerative brain disease chronic traumatic encephalopathy, and his attorney said Thursday that the player’s daughter is suing the NFL and the New England Patriots for leading Hernandez to believe the sport was safe.

In a news conference at his offices, Hernandez’s attorney Jose Baez said the testing showed one of the most severe cases ever diagnosed.

“We’re told it was the most severe case they had ever seen for someone of Aaron’s age,” Baez said.

Dr. Ann McKee, the director of the CTE Center at Boston University, concluded that the New England Patriots tight end had stage 3 of 4 of the disease, and also had early brain atrophy and large perforations in a central membrane.

The lawsuit filed in federal court in Boston on Thursday claims that the team and league deprived Avielle Hernandez of the companionship of her father. It is separate from a $1 billion settlement in which the league agreed to pay families of players who suffered brain damage because of repeated head trauma while playing football.

NFL spokesman Brian McCarthy declined comment, saying the league had not seen the lawsuit.

Baez said Hernandez had been playing football because the NFL led him to believe it was safe.

“Those representations turned out to be false,” Baez said.

CTE can be caused by repeated head trauma and leads to symptoms like violent mood swings, depression and other cognitive difficulties. Hernandez killed himself in April in the jail cell where he was serving a life-without-parole sentence for a 2013 murder. His death came just hours before the Patriots visited the White House to celebrate their latest Super Bowl victory.

CTE can only be diagnosed in an autopsy. A recent study found evidence of the disease in 110 of 111 former NFL players whose brains were examined.

CTE has been linked with repeated concussions and involves brain damage particularly in the frontal region that controls many functions including judgment, emotion, impulse control, social behavior and memory.

“When hindsight is 20-20, you look back and there are things you might have noticed but you didn’t know,” Baez said.

A week before his suicide, Hernandez was acquitted in the 2012 drive-by shootings of two men in Boston. Prosecutors had argued that Hernandez gunned the two men down after one accidentally spilled a drink on him in a nightclub, and then got a tattoo of a handgun and the words “God Forgives” to commemorate the crime.

Baez said he deeply regretted not raising the issue of Hernandez having CTE during his murder trials. He said they did not blame CTE for the murders because Hernandez’s defense was actual innocence.

A star for the University of Florida when it won the 2008 title, Hernandez dropped to the fourth round of the NFL draft because of trouble in college that included a failed drug test and a bar fight. His name had also come up in an investigation into a shooting.

In three seasons with the Patriots, Hernandez joined Rob Gronkowski to form one of the most potent tight end duos in NFL history. In 2011, his second season, Hernandez caught 79 passes for 910 yards and seven touchdowns to help the team reach the Super Bowl, and he was rewarded with a $40 million contract.

But the Patriots released him in 2013, shortly after he was arrested in the killing of semi-pro football player Odin Lloyd, who was dating the sister of Hernandez’s fiancee. Hernandez was convicted and sentenced to life in prison; the conviction was voided because he died before his appeals were exhausted, though that decision is itself being appealed.