Why does K grab a gun before the past is changed?

Question

After J hangs up on K in a phone argument, K opens his arsenal, chooses a weapon, sits in his chair and then disappears.

IMHO, K seems to know what is about to happen, but arming himself appears futile.

Is there any reason K would do this?

Answer 1

If you mean by K knew what is about to happen the time traveling by Boris to kill K, I doubt it. I think K just assumed Boris might appear to kill him again, since he was pretty chafed with K. I think an agent like K should be ready for this type of attack, when the enemy is also like Boris the Animal. So he kept himself ready for an imminent attack from him. Also for your note the only trace for K to find that Boris is going to time travel to kill K in past, was the statement by Boris You don't know it, K, but you're already dead. But when he said that K was down on the street and Boris was on the building talking it like a soliloquy . So it was impossible for K to hear that.

Answer 2

K knew that his time was coming to see "Just Boris", again. And as he stated "If he had to do it again, he would have killed him the first time". He was getting ready for that by opening his arsenal, he just didn't know how he was going to be approached by Boris. This is what creates the past for K knowing J from childhood...He just couldn't ever talk to him about it until after it had happened.