Given the following context:

A suicide bomber detonates himself at a party in Java, Indonesia, and a Javanese Sultan's daughter, Sultana, is believed to be one of the unidentified victims. Jake Travers, an American posing as a graduate student from Cornell University, was at the scene of the blast and is held as a witness by a police detective of Detachment 88, Lieutenant Hashim. 
After interviewing Jake at the crime scene, Hasim and Jake are attacked by terrorists led by Malik and his henchman Achmed. Jake saves Hashim and kills two terrorists, but Achmed manages to escape. Hashim becomes suspicious after he observes Jake's combat skills. Jake and Hashim are brought to the hospital where Hashim's wife meets Jake. At Hashim's wife's insistence, Hashim invites Jake to their house for breakfast. At the house, Hashim tells Jake that he ran a background check on him through Interpol. Jake tells Hashim he is an FBI agent conducting an undercover investigation, and suggests they cooperate with one another. 
Returning to his apartment, Jake faxes to a friend stateside a photo of a tattoo from the corpse believed to be Sultana's. Jake's friend informs him that the tattoo is typically used by Chinese high-class prostitutes, which confirms Jake's suspicion that the body is not Sultana's.
Jake follows a lead to a night club, where he brings home a prostitute bearing a similar tattoo. When the prostitute cooperates with Jake, they are ambushed by Hashim's terrorists and a Chinese gang operating the prostitution ring. The police, who had been covertly surveilling Jake, intervene and suffer casualties in the fight. Jake flees the scene, but the police eventually capture him.

answer the following question:

Who begins to suspect an American posing as a graduate student after observing his combat skills? 

Lieutenant Hashim