The attack on Gotham was a major attack led by a resurrected Jerome Valeska and his devoted followers. The incident lasted a night where mass property damage was caused and people died. The event was originally going to cultimate with the execution of Bruce Wayne until he managed to defeat Jerome.
Followers of Jerome Valeska led by Dwight Pollard stole the corpse of Jerome from a warehouse owned by Wayne Enterprises, where Dwight then planned to use his knowledge of the experiments that occurred at his previous employment Indian Hill to bring Jerome back from the dead. The resurrection would prove to be a success, however Jerome blew up a generator to the city and killed Dwight, which led to a city wide blackout. Prior to the detonation, Jerome broadcast a live report across the televisions in Gotham urging his followers as well as other citizens to take part in the chaos.
The devoted followers and some citizens took the streets and took part in riots, which involved murder and property damage. The Gotham City Police Department fought back against the attacks, which was also brought to their precinct. The Court of Owls were close to intervening, but were called off by their member Frank Gordon who wanted to allow his nephew detective Jim Gordon and the GCPD to prove themselves in dealing with the incident.
Jerome kidnapped Bruce Wayne and brought him to a carnival where he planned to kill the boy, fulfilling an original mission he was unable to do due to being betrayed and killed by his mentor Theo Galavan. During Bruce's captivity at the carnival Jerome told him that there were no more heroes in Gotham. Jerome was close to firing a canon in Bruce's face, but Bruce managed to pick the handcuffs tying him to the pole and escape and Gordon and Alfred Pennyworth arrived to stop the maniacal followers.
Bruce and Jerome faced off in a glass house, where Bruce managed to gain the upper hand and beat Jerome to a bloody pulp, however chose to spare his life. Jerome tried to attack Bruce, but was beaten down by Gordon and taken into custody. By sunrise the horror was over, with those who took part in the incident being rounded up and arrested.
Days following the incident, bodies left over were still being found which caused a strain on the police department's resources.