Ever since Klaus turned off his humanity 3 months ago people thought he wouldn't know how to keep himself in check. Caroline taught him this art when she turned her own humanity off after her mother died.
Caroline turned it on again after a year went by like she said she would. While everyone else tried desperately to have her turn it back on; Klaus understood the grief she wanted to go numb for. He out of all of them knew what she felt; being over a thousand years old gave him such insight.
Caroline and Klaus had been on a mission to find the solution to her daughter's covens curse. Until three months ago when they were both researching a plausible solution and got attacked by a triad of people who were waiting for them.
They had a coven of witches doing their bidding and they managed to subdue Klaus. Rebeka managed to help Klaus and escape while Elijah kept their attackers at bay. Unfortunately, that outcome led to this moment.
Klaus called in his general, "it's time" was all that needed to be said. His general nodded his head and walked away calling out the orders.
As the first wave hit Klaus was front and center. He half shifted beast, running through killing people in his path.
Klaus managed his way into the establishment. Using his senses he picked up his mates sent. He ran in her direction to crash to a halt when he was witnessing what was before him. His Caroline attached to tubes inside a gel liquid on view for the world to see.
Klaus's anger mutilated the yellow irises to a crimson red. Through the bond, he sent a wave of heat to comfort her. She, in turn, shuddered behind the glass. Sending warmth back. Reality set in when the lights shut down. Then the pulsating feeling overcame him and bought Klaus to his knees in front of his beloved.
Though there were no lights Klaus can still see in sheer vividness the troops swarming in to subdue him further. His last gasp and moments ended while he inhaled his mates sent one last time before seeing black.