In general, football is a sport that prides itself on violent collisions and bone-crushing hits. On the compressed, 50-yard field of arena football, the collisions are often faster and the hits harder, but it was a relatively quiet play that took the life of Al Lucas last week.

Lucas, a lineman with the Arena Football League’s (AFL) Los Angeles Avengers and former National Football League (NFL) player, collapsed on the field after trying to make a tackle on a kickoff return.

He was taken off the field in a stretcher, but few in the stadium were prepared for the post-game news. Lucas never moved again, and was pronounced dead at the California Medical Center in Los Angeles. He is believed to have suffered a trauma-inducing blow to the head.

“I watched it, and it seemed like the same old thing you see all the time,” Brentson Buckner, Lucas’ former teammate with the NFL’s Carolina Panthers, told The Washington Post. “I’ve seen harder licks before, harder collisions. You look at it and you know what kind of powerful guy he is, and you don’t think anything bad should have happened to him.”

Lucas’ agent told reporters that the player had no previous medical condition that would serve as a precursor of this tragedy.

“I am just speechless,” Virgil Adams told the Post. “I’ve been in a fog ever since it happened. We’re still finding out what happened. I don’t know what to say. I’ve seen the replay several times, and it just looks like he suffers a blow to the head. But it doesn’t look like it’s anything out of the ordinary, and there was nothing going on with Al medically before this incident. We’re still basically clueless. We’ll just wait for the autopsy and try to figure out what happened.”

The AFL, which in the absence of knowledge of Lucas’ condition decided to continue the game, is also searching for answers.

“When you think of the number of players who play this game and the number of spinal cord injuries that happen, there are relatively few,” Troy Vincent, a member of the NFL’s Buffalo Bills and president of the league’s player’s association, which has organized a body for Arena players, said in a statement. ”It is a violent sport that we choose as men, and that we as parents allow our children to play.”

“[You can’t] prevent it,” he continued. “The player has to play. You need to teach people and educate people and coach people about the right way to play and the proper technique to tackle. Obviously we will talk about doing everything we can to make our sport as safe as possible. But I don’t know how much more you can do.”

Those closest to Lucas’ said that his loss would be hard to swallow, especially considering that it occurred while he was playing the game he loved.

“He was always a fun-loving guy,” Buckner told reporters. “He was always laughing and joking. In training camp, everyone would be tired and it would be quiet, and you’d hear someone coming down the hall being loud and telling jokes, and it would be him. When I heard about it, knowing Al and knowing what kind of person he is and knowing he’s married and has a little girl, it was heartbreaking to me.”