Mat 22:6 And the rest took his servants, and treated [them] spitefully, and slew [them].
Mat 22:7 But when the king heard, he was angry: and he sent out his armies, and destroyed those murderers, and burned up their city.

Both this parable and the previous one about the vineyard owner and his renters come to a very bloody end. Christ makes his points as dramaticaly as possible. In the previous verse, the vineyards owner's servant, his son, and the renters all ended up dead. Here, the kings servants and the invited guests as all killed and their city burnt. These particular parables are like Shakespearean tragedies where the main actors all end up dead. Only the owner/king is left alive at the end.

Notice that Christ is not condemning the violence on the part of the owner/king. Indeed, he is justifying it. Many modern Christian clerics may condemn the death penalty for murderers, but Christ took it for granted that those who killed would end up dying at the hands of those who help power. Remember, Christ likens the kingdom of heaven as the universal rule to this ruler and what he does.

Notice the pattern. The last verse was about they way the invited guests rejected the relationship and pursued their own interest. The king also reacts emotionally to the guests message. Here, Christ is saying that this emotional rejection leads to death.

Notice again the three steps in the actions taken by both the invited guests and king. The invited follow the pattern of physical (taking), mental (treating spitefully), and ending with emotional (killing.) The king's pattern is a different. He sent his army (mental), then killed (emotional), and then burned the city (physical).

"Took" is from krateô, which means "rule," "hold sway," "conquer," "prevail," "lay hold of," "secure," "control," and "command."

"Treated spitefully" is from hubrizô, which "to treat despitefully," "to outrage," "to insult," and "to mistreat."

"Slew" is from apokteinô, which is a stronger form of the verb "to kill" and "to slay."

"Angry" is from orgizo, which means "to be made angry," "to be provoked to anger," and "to be irritated."

"Sent out" is from pempô, which means "to send," "to send forward," "to shoot," and "to escort."

"Destroyed" is from apollumi, which is a very string form of "to destroy," "to kill," "to slay," and "to lose." It is translated as "lost" and "perish" elsewhere in Matthew. It means "to destroy utterly." It also means "to ruin" a woman.

"Burned" is from emprêthô, which means "to blow up," "to inflate," and "to burn."