I don't even think there is any difference between Rick and Sean in essence. If Rick in the third season is put into the first season, I believe he will refuse to go back to rescue Moore like Sean.
Slowly, Rick lost his trust in people.
Although Andrea's implementation was accidental after Herschel's farm was captured, when a group of people came to the supply warehouse and Brother Crossbow said that he would go back to find Andrea, Rick made it clear that it wouldn't work.
I think Rick may have done the same in the past, but he will never be so decisive. Killing Sean changed Rick, just like killing Otis after Sean. We all know that when Rick slowly approached Sean and slowly reached for Sean's gun. Sean has begun to hesitate. He tried to put down his gun. Even if Rick saw this hesitation, he didn't choose to give Sean another chance.
Because Sean stepped forward several times, it caused a crisis to the team. Maybe, as Dell said, the team has broken up. Rick tried to save the team, and killing Sean might be the last resort. Rick killed Sean, in a sense, not to protect himself, but purely to kill him. Rick finally found the crack in his inner defense, and he didn't hesitate.
Then, after the capture of the prison in the first episode of the third season, Rick himself put forward the idea of "killing all prisoners". After the prisoner leader showed bad intentions to Rick and his party, Rick did not hesitate to kill those people.
And one of the fugitives was attacked by zombies, and Rick didn't open the door to give him a chance.
This series of changes happened in the first episode of the third season, and it seems that the screenwriter is deliberately announcing it to the audience.
This season, Rick will adapt to the world more.
Too many times witnessed the evil of human nature, witnessed the horror of the zombie world, Rick has changed. In Rick's world, others are more and more like opponents than partners, and he refuses to cooperate with strangers.
As Maggie told Glenn after being taken away by the governor, fighting zombies too many times made us forget the ugly face of people. Rick didn't forget, so in his eyes, there are more and more strangers and enemies, and fewer and fewer partners. He paid more and more attention to his teammates and refused to help strangers.
In fact, anyone who tries to survive in such an environment may become like Rick. As Sean said, the world has changed, and the old one is not working.
Relatively speaking, Brother Crossbow's thoughts are much freer. In brother crossbow's eyes, there is not so much consideration. Brother crossbow always chooses what he thinks.