Cop Killer

A Cop Killer is, as the title suggests, a person who kills at least one person working in the local police force. Usually, when a cop is murdered, the rest of the police force makes hunting the perpetrator down a top priority, as they intend for their colleague's death to not go unpunished.

Criminal Minds
''Usually, whenever a policeman is killed on the show, it is usually incidental and not intentional. One example of the contrary is Animal. Some known cop killers on the show include:''
 * Phillip Dowd ("L.D.S.K.") - Dowd sniped a policeman who leaked information of the investigation to the press, as he was being arrested under suspicion of being the unsub.
 * Vincent Perotta ("Natural Born Killer") - Some of Vincent's victims have been seen to be policemen. Vincent also attempted to kill an undercover cop, but he was rescued.
 * Cally's Tribe ("The Tribe") - While approaching the house of their soon-to-be victims, the Minton family, the tribe was forced to kill a policeman who was assigned to spy on the family.
 * Francis Goehring ("Identity") - When he was cornered by three policemen, Goehring decided to commit a suicide attack, which only succeeded in killing one of them along with himself.
 * Jason Clark Battle ("Lucky" and "Penelope") - While stalking Garcia after finding out she survived him, Battle calmly walked towards a policeman assigned to protect her and Morgan and shot him twice in the chest.
 * Owen Savage ("Elephant's Memory") - After killing Rod Norris with a planted bomb, Owen waited for his father Lou, a police deputy, to respond to the bombing. When Lou and another policeman were the first officers to respond, Owen attacked them with an assault rifle he stole from Lou, killing both.
 * Steven Fitzgerald ("In Heat") - At the beginning of the episode, Steven murders a gay man he befriends, Charles Luvet, who was a vacationing New Orleans police detective.
 * Animal ("Brothers in Arms") - Animal dedicated most of his killings to murdering those he saw as figures of authority: police officers. He successfully managed to kill four.
 * George Foyet ("Omnivore", "...And Back﻿", "Nameless, Faceless", and "100") - In Omnivore, when Morgan and a Boston policeman raided one of his homes to look for him, Foyet ambushed the latter outside and killed him by apparently stabbing him to death.
 * Dale Shrader ("Retaliation") - When his partner Joe Muller sent the police cruiser containing him, Prentiss, and a police detective crashing down a hillside as part of an escape plan, Dale recovered from the crash quickly and strangled the detective to death before stealing the keys to his handcuffs.
 * Connor O'Brien ("Public Enemy") - After killing a flower salesman at a marketplace, Connor stayed behind at the crime scene, apparently to feed off of the crowd's fear, when he was spotted by a policeman he knew while attempting to flee, forcing him to stab him repeatedly in the neck and collar when he tried to detain him.
 * Ronald Boyd ("A Rite of Passage") - Devolving into a spree killer, Boyd lured his boss into a secluded area before shooting her to death. Then, while attacking the Lugo Cartel with a shotgun, he murdered the deputy accompanying him with a revolver when he witnessed the massacre.
 * Billy Flynn ("Our Darkest Hour" and "The Longest Night") - After luring Morgan and Detective Matt Spicer into a trap using Spicer's sister and daughter in Our Darkest Hour, Billy knocked Morgan out briefly before goading Spicer into surrendering by threatening to shoot Ellie. When Spicer caved in to the demands, much to Morgan's distress, Billy shot him in the chest at point-blank range.
 * Shelley Chamberlain ("Hanley Waters") - While stopping at a road block, Shelley went into a fit of rage and shot a policeman when he attempted to force her out of her vehicle. She then hit another policeman with her car as she escaped. The policemen were last confirmed to be in critical condition, but it is unknown as to whether any of them survived their wounds. If they didn't, Shelley would be officially classified as a cop killer.
 * Daniel Dryden ("Killer Profile") - As he prepared to kill his eighth victim (via premature burial in a coffin), Daniel was spotted by a police detective, who apparently pieced together that he was the killer, forcing him to kill the detective and knock him on top of the coffin the victim was still in before filling the hole.

Real World

 * 2009 Oakland shootings
 * 2009 Pittsburgh police shootings
 * Lakewood police officer shooting