In the first half of Perek 4 it tells us that G-d was very angry.  G-d was so angry that he allowed enemies to attack. Other nations could not believe this. In the second half it blames the leaders and says that the destruction was caused because of the leader's sins.
    It goes on to say something very interesting. In Pasuk 14 it says that the people walk blindly through the streets. What it is actually trying to say is not that the people were actually blind, but they could not see what that they were listening to false prophets. It also goes more in depth about why Yerushalyim was destroyed. When things went wrong or they were having trouble with  something, they would not turn to G-d for help. Even worse, they would turn to other nations for help.
     It also talks about the gruesome mothers who ate their children, which was also mentioned in Perek 2. The Perek ends off being a little bit hopeful. It says that the punishment of the people is almost finished and that the people who attacked them, are going to be punished now.