New Jack City

Nino Brown and his gang, the Cash Money Brothers, become the dominant drug ring in New York City once crack cocaine is introduced to the streets during the late 1980s. His gang consists of his best friend, Gee Money; enforcer Duh Duh Duh Man; gun moll Keisha; Nino's girlfriend, Selina, and her tech-savvy cousin, Kareem. Nino converts the Carter, an apartment complex, into a crack house. Gee Money and Keisha kill rival Fat Smitty, the CMB throws out the tenants, and Nino forces the landlord out onto the streets naked. Undercover detective Scotty Appleton attempts to make a deal with stick-up kid Pookie, but Pookie runs off with the money. Scotty chases Pookie and shoots him in the leg, but the police let him go.
When Det. Stone comes under pressure, Scotty volunteers to infiltrate Nino's gang and is partnered with loose-cannon Nick Peretti. Elsewhere, mobster Frankie Needles attempts to collect taxes from Nino, who refuses to pay. While Scotty and Nick spy on Nino and his gang as they hand out Thanksgiving turkeys to the poor, Scotty spots Pookie, now a crack addict, as Pookie beats his junkie girlfriend. Instead of arresting him, Scotty puts Pookie in rehab, and, later, Pookie offers to help bring down Nino. Against his better judgment and the disapproval of Stone and Peretti, Scotty recruits Pookie as an informant in the Carter.
When Pookie relapses, Gee Money realizes that he is wired, and he orders the Carter destroyed. The cops find Pookie's bloody corpse, but it is booby-trapped; Nick defuses the explosives mere seconds before it explodes. Angry, Nino warns Gee Money not to make such a costly mistake again. After Pookie's funeral and no longer needed by Stone, Scotty and Nick go undercover as drug dealers. After bribing Frankie Needles, Scotty infiltrates the CMB due in part to Gee Money's increasing ambition and drug use. Though Nino distrusts them, he agrees to do business. After relating an anecdote about his own violent initiation into a gang, Nino warns that he will kill both Scotty and Gee Money if there are any problems.
Scotty gains Nino's trust when he reveals information about Gee Money's side deal and saves Nino from a gun-toting old man who had earlier attempted to convince the police of Nino's destructiveness. While Nino, Scotty, and the CMB attend a wedding, Nick sneaks into Nino's mansion to collect evidence, and Don Armeteo sends hitmen to assassinate Nino; a massive shootout erupts between the CMB and hitmen. When Nino uses a child as a shield, Scotty attempts to shoot Nino behind his back. Keisha is gunned down as she sprays bullets into the hitmen's van as they escape. Later, Selina condemns Nino for his murderous activities, and Nino throws her out. Nino later kills Don Ameteo from a speeding motorcycle.
Stone, Scotty, and Nick arrange a sting operation to nab Nino. Kareem, who knows that Scotty and Pookie are connected, blows Scotty's cover, and a shootout ensues. Nick saves Scotty by killing the Duh Duh Duh Man, and Nino escapes. That night, Nino confronts Gee Money, who accuses Nino of egotism, and Nino regretfully kills him. After the gang's collapse, Nino holes up in an apartment and continues his criminal empire solo. Scotty and Nick assault the complex, and Scotty brutally beats Nino, revealing that it was his mother that Nino killed in his gang initiation. Nick talks Scotty out of killing Nino, who is taken into custody amid threats of retaliation.
At his trial, Nino pleads guilty to a lesser charge, claims to have been forced to help the gang due to threats, and identifies Kareem as the leader. When Nino is sentenced to only one year in jail, Scotty is outraged. As Nino speaks with reporters outside of the courtroom, the old man again confronts Nino and shoots him in the chest. Scotty and Nick are both satisfied as Nino falls over the balcony to his death. As onlookers look down at Nino's body, an epilogue states to the viewers that decisive action must be taken to stop real-life Nino Brown analogues.

Question: Who blows Scotty's cover?
Answer: Kareem