CLYDE: He tried to kill me! Why'd he try to kill me? I didn't want to hurt him…. I ain't against him. I ain't against him.
Clyde says this right after he tries to rob a grocery store and the butcher attacks him with a meat cleaver. He is shocked that someone would try to kill him just for stealing a few food items from the store. But, to escape, he also hits the butcher, injuring him enough for him to be hospitalized. From this point on, the crimes and the violence will escalate.
CLYDE: This afternoon, we killed a man, and we was seen…and that's murder and now it's going to get rough.
When a bank hold-up goes awry, Clyde impulsively kills the manager. Bonnie doesn't seem to be too bothered by this, but Clyde realizes that things are going to get much more difficult for them. In addition to being a thief, he's now a murderer.
BUCK: Listen, it was either you or him, wasn't it?
BUCK: The guy that you killed—it was either you or him?
CLYDE: He put me on the spot.
BUCK: You had to.
CLYDE: I had to.
When Buck and Blanche join the gang just after the murder, Buck questions Clyde about the murder, probing for a justification. Clyde makes it seem like self-defense, which is clearly untrue. The man he killed was unarmed. After this, Clyde begins to see more of the killing he does as self-defense, whether it is or not.
CLYDE: Hey. Hey. The laws are outside. They're blocking the driveway.
Now that the gang is wanted for murder, the law steps up its efforts to capture the gang dead or alive. After getting a tip-off from a delivery boy, law enforcement officers descend on a house the gang is staying in. By now, the gang has a whole assortment of guns to use to fight back. In the violent encounter that takes place, two policemen are killed. The violence escalates dramatically.
BLANCHE: I didn't marry you to see you get shot at. Please let's go, let's leave, let's get out of here…
BUCK: I can't. I killed a guy. Now we're in this.
Blanche pleads with Buck to leave the gang. But Buck knows that, since he's now killed someone (and a policeman at that) there is no turning back. He digs in deeper, and so does the law. Subsequent encounters will only get bloodier.
BONNIE: C.W., C.W.—grenades.
As Bonnie's mid-raid line lets us know, the gang is prepared for the law, not only with machine guns but now also with grenades. In this raid and the pursuit immediately afterwards—the bloodiest encounter yet—Buck's killed, Blanche's wounded and captured, and Bonnie and Clyde are wounded. But, along with C.W., they manage to escape. The escalating violence has reached yet another level.
HAMER: I figure to have my picture took with them two just one more time.
As another law officer looks at the photo the gang took of Frank Hamer with Bonnie and Clyde, Hamer makes this comment. He clearly isn't interested in capturing the two alive. He wants them dead, and he wants to have his picture taken with him the way a big game hunter might have a picture taken with a trophy kill.
MALCOLM: You just be sure you're off the streets in that town when they get in their car.
After he's told Hamer of Bonnie and Clyde's whereabouts, Malcolm tells C.W. not to get back in Bonnie and Clyde's car with them when they leave town the next day. He, of course, knows the plan to bring down Bonnie and Clyde.
BONNIE: Hey, isn't that Malcolm there?
These are Bonnie's last words. She says them as they see Malcolm standing next to what looks like a flat tire. Clyde gets out to help, and he and Bonnie are both killed in a hailstorm of bullets in the film's final ambush—in many ways, the most violent and shocking scene of all.