CO2 couldn't kill these two polar bears, but gunshots from kayakers and researchers did kill them

Polar bear shot after dragging off Svalbard paddler : Views and News from Norway

The expedition, called Svalbard 360, came to an abrupt end when the polar bear attacked while they were sleeping in their tent. Officials said Ludvig Fjeld, from Sarpsborg in southern Norway, more than likely saved the life of his expedition partner Sebastian Plur Nilssen of Fredrikstad, who suffered lacerations on his chest, head and neck.
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A hospital spokeswoman described his injuries as “moderate to severe” but said they were not life-threatening. The two men had told newspaper Fredrikstad Blad in June that they were aware there could be “a whole lot” of polar bears on Nordaustland and had hoped to avoid using firearms to keep the bears away.

Police Chief Inspector Per Andreassen of the governor’s office on Svalbard (Sysselmannen på Svalvard) told Svalbardposten that Fjeld said the polar bear released Nilssen after his first shot, but he kept firing. Andreassen said the bear was hit by four shots.
...Another recent shooting remains under evaluation, after a polar bear was found dead and determined to have been shot but only wounded on July 8. The bear is believed to have died several days later and was found on July 20.

An investigation revealed that four researchers [what were they researching?] on Svalbard had felt threatened by the bear at their workstation at Hyttevika all day on July 8. “They tried scare off the bear several times, without much luck,” reported the governor’s office this week. “The polar bear finally came right up to their cabin and after a while, one of the researchers opened the door and fired a shot with his rifle.”

It’s since been determined that shot later killed the bear. The researcher who fired the shot is being called into a formal hearing before the case will be sent to the prosecuting authorities