Buffalo Bills safety Damar Hamlin, who has been cleared to resume football activities, said Tuesday his cardiac arrest during an NFL game in January was caused by commotio cordis.

Hamlin went into cardiac arrest after making a tackle and appearing to be hit with a helmet in his chest during the first quarter of the Bills’ game against the Cincinnati Bengals on January 2.

Commotio cordis can occur when severe trauma to the chest disrupts the heart’s electrical charge and causes dangerous fibrillations.

“I died on national TV in front of the whole world,” Hamlin said in his first session with reporters since the injury. “I lost a bunch of people in my life. I know a bunch of people who lost people in their lives. I know that feeling. That right there is the biggest blessing of it all – for me to still have my people and my people to still have me.”

The 25-year-old has been at the Bills’ practice facility in Orchard Park, New York, participating in voluntary offseason workouts this week, according to the team.

“He is fully cleared,” Bills General Manager Brandon Beane told reporters. “He’s here.”

Hamlin said he was blessed to have a wonderful medical staff who “treat me with the care of their children.”

The safety said his heart is still in the game and he was announcing his comeback to the NFL.

“I just want to show people that fear is a choice. You can keep going at something without having the answers and without knowing what’s at the end of the tunnel,” he said. “You might feel anxious – you might feel any type of way – but you just keep putting that right foot in front of the left one and you keep going. I want to stand for that.”

Beane said that Hamlin had seen three separate specialists over the offseason, who all agreed that the player “is clear to resume full activities just like anyone else who was coming back from an injury.”

“(Hamlin’s) in a great headspace to come back and make his return,” Beane added.

Bills head coach Sean McDermott said the team is happy that Hamlin is back.

“We’re super excited for Damar. He’s moving forward one step at a time here. He’s been cleared from a physical standpoint,” McDermott said.

“We’ll provide all of the mental help we can from a mind, body and spirit standpoint so just happy for him that he’s been able to check some of those boxes to this point and we’re moving forward taking it one day at a time.”

According to the American Heart Association and the American College of Cardiology, if no underlying cardiac abnormalities are discovered through testing, athletes who have been resuscitated from commotio cordis may return to playing.

Hamlin likely went through a lot of tests, including electrocardiograms and echocardiograms, before doctors cleared him to return to training.

“What it basically means a few things. One is that his heart function returned to normal. He has no underlying problems with the anatomy of the heart itself, and he has no underlying electrical problems, so that’s the most important thing – and the way they figured that out over the last three-and-a-half months was to do a lot of tests,” CNN Chief Medical Correspondent Dr. Sanjay Gupta said on “CNN News Central.”