JUNE 7, 12:00pm: Thompson is now awake and responsive, per his agent. Pelissero echoes the sentiment that Thompson has a positive prognosis, a welcomed update to this situation.
JUNE 7, 8:58am: An update from Thompson’s agent states (via Pelissero) that he remains unconscious but in stable condition with “good” vital signs. Further developments related to his condition and recovery timeline (about which, ESPN’s Jeremy Fowler notes, doctors are “optimistic”) will no doubt be closely monitored around the NFL.
JUNE 6: The Chiefs canceled their scheduled practice Thursday due to a medical emergency, as first reported by ESPN’s Adam Teicher. Details on the situation have since emerged. 
The incident took place during a special teams meeting with the affected player suffering a seizure and going into cardiac arrest, per Tom Pelissero of NFL Network. The identity of the player was initially unknown, but both Pelissero and Teicher have since noted it is defensive end BJ Thompson.
Thompson received immediate attention from the Chiefs’ medical staff and he was taken by ambulance to a local hospital. He is in stable condition, per multiple reports. In the wake of that encouraging update, Teicher adds Kansas City will practice tomorrow as the team’s OTAs wrap up.
Thompson was a fifth-rounder of the Chiefs during last year’s draft. He began his college career at Baylor, collecting four sacks in 2018. He then transferred to Stephen F. Austin and spent four years there. The 6-6, 243-pounder earned first-team All-WAC honors in 2021 and ’22 to close out his tenure at the college level.
The 27-year-old made just one appearance during his rookie campaign, the regular season finale. He made a pair of tackles while seeing a rotational defensive role along with time on special teams. Thompson once again has a number of players ahead of him on the depth chart (George Karlaftis, Mike Danna, Charles Omenihu, Felix Anudike-Uzomah), and today’s events will no doubt keep him sidelined for a period of time. Thompson’s recovery process will be worth watching ahead of training camp next month.