Donnovan Hill, who was paralyzed as a football player at age 13 and became a catalyst for safety protections in the youth game, died Wednesday after complications from surgery related to management of his injury, according to his mother, Crystal Dixon.The former Pop Warner star from Lakewood, California, a bedroom community near Los Angeles, was 18. In January, Hill had reached an unprecedented settlement in a lawsuit he had filed against the national office of Pop Warner, which he alleged had failed to take proper measures to ensure his coaches were trained. Hill was paralyzed in 2011 making a tackle at the goal line during a regional Pop Warner championship game, using a headfirst technique that he says was promoted by his coaches.Terms of the seven-figure settlement were not disclosed, by agreement of the parties. But it helped open the door for another multimillion-dollar settlement against Pop Warner a month later, by a Wisconsin family that alleged that their son, who killed himself at age 25, had suffered from a lack of protections provided by Pop Warner. An autopsy found he had chronic traumatic encephalopathy, or CTE, a brain injury associated with repetitive head trauma and athletes in contact sports.Dixon said Hill had been admitted to the hospital Tuesday for a routine procedure, to clean out a skin graft related to pressure sores from his lower body being unable to move. As he was wheeled into the operating room, Dixon said Hill told her and other family members on site, "I love you all." Dixon said she responded that he didn't need to say that, that he'll be back out soon. Hill said, "I just want to say, I love you all."That was Dixon's last conversation with her only son. She said she was told that during the surgery, the doctor accidentally cut an artery, and as he lost blood, he fell into a coma. He died Wednesday at 4:35 a.m., she said. Spokespeople for the hospital were unavailable to confirm details of his death.Dixon said that in recent months, life had improved for Hill. In response to Outside the Lines stories about Hill showing he and his mother struggling with substandard equipment, strangers had donated a motorized wheelchair and handicap-accessible van. A month ago, Dixon and Hill moved out of her mother's apartment and into their own in anticipation of the settlement funds becoming available. Dixon said she has not received any of the settlement money to date, as lawyers sort out liens on prior medical bills.Dixon said he was busy writing poetry and song, and that he recently had been working out twice a week with the limited strength he had in his arms. Tuesday before heading to the hospital, Hill wrote on Twitter (@hill_donnovan), "Minor surgery today #PRAY4VIZZY" -- one of his nicknames. It was his last tweet.Hill's settlement came in the wake of a December ruling by a California judge that cleared the way for Hill to proceed to trial, which had been set to start May 11. Los Angeles Superior Court Judge Richard Shaller had rejected Pop Warner's argument that the lawsuit should be thrown out because Dixon had signed a pre-participation waiver acknowledging the risks of playing football.A two-way star for his Lakewood, California, program, Hill came up from his safety position to try to stop a ball carrier at the goal line. The running back went low and led with his head, as did Hill. The collision snapped Hill's neck.Hill's lawsuit alleged that his coaches encouraged headfirst tackling. He said he was punished when he objected to use of that technique in practice, and that he deployed it in games with no repercussions. In an Outside the Lines TV story in 2013, his coaches offered conflicting accounts on whether they encouraged headfirst tackling, with head coach Sal Hernandez saying he warned Hill against using it and assistant coach Manny Martinez defending the use of that technique.More broadly, the lawsuit revealed the lack of safety protections facing all participants in Pop Warner. Founded in 1929, Pop Warner advertises itself as a safety-first organization in which children play for coaches trained in proper tackling technique. But in a deposition, executive director Jon Butler conceded that the national office does not check whether coaches in fact receive such training.Hernandez, a barber, told Outside The Lines that he took Pop Warner's mandatory course for head coaches but said in his deposition that he never followed through. Martinez, a Hollywood actor, also received no training.Pop Warner and lawyers for the coaches argued that their behavior didn't rise to the level of gross negligence, the standard that must be established to take civil action against volunteer coaches. The judge declined to adopt that position or dismiss the national office from its exposure, underscoring the responsibility of national organizations to enforce rules they promulgate at the community level.The settlement also resolves a related class-action lawsuit filed by Dixon, alleging she and other parents were misled by Pop Warner about the safety of their children playing the sport. Even after Hill was injured, Pop Warner continued to state on his website that no player had ever been catastrophically injured. The organization serves 325,000 football players and cheerleaders between the ages of 5 and 16."Any governing body in the youth sports industry, especially those in contact sports, should be paying attention," Hill's lawyer, Rob Carey,said after the judge's ruling in December. "They need to know that if they make representations about safety or training, it better be true. And if you know of risks of playing a game, take all reasonable precautions to make sure those risks are mitigating. In a football context, that means training coaches in tackling, at a minimum."Hill was at heightened risk of paralysis because of a congenital narrowing of the bones in the neck, his mother told ESPN in 2013. But that was not discovered until after he was injured; the standard, simple pre-participation physical exam that players undergo does not check for as much. Thus, he was more susceptible to catastrophic injury, which is rare in football, at least before high school."The issue couldn't be more simple -- authorities and coaches have a responsibility to players," Carey added. "The authorities of youth sports leagues must be vigilant in their training of coaches, because keeping the game safe is what's most important. Sadly, we've seen what happens when these entities fail to uphold that responsibility."The lawsuit also exposed the financial vulnerability of all of youth football's key parties in the case of a serious injury. In an interview last June, Dixon said Hill and his family had received no financial support from Pop Warner to date. Even with state assistance, they lacked the funds to purchase an electric wheelchair or handicap-accessible van, among other basic needs.According to attorneys, Donnovan's case will set an important legal precedent that will be advantageous to many players."Donnovan's case will have an impact on young athletes for generations," Carey said. "It will help ensure that those in charge of safety -- from directors and coaches to whole organizations -- will not be allowed to shirk their duties or avoid responsibility."