Raised in a family that valued education -- his older brother has two master's degrees, and his older sister has a doctorate -- Clark went on to earn a bachelor's degree in police science at night school from John Jay College.
And as he climbed the police ladder, it became more evident to Clark that drugs were the illness that destroyed neighborhoods. "Drug dealers are murderers, man," he said simply.
Recognized as thorough, smart and energetic by his supervisors, Clark was promoted to commander of the 47th precinct -- where he grew up -- in 1998.
Clark brought with him a desire to combat drugs and build stronger community ties. After a year as the 47th's commander, Clark had reduced overall crime by 13 percent. By the time he left in 2000 to lead another precinct, crime had dropped overall by 26 percent. Homicides had dropped in 1999 to just nine, spiked to 29 in 2000 and then dropped again a year later after Clark had targeted likely triggermen.
Clark said he was able to reduce overall crime by picking the right people for the right jobs and earning the support of his troops -- while pleasing his commanders with hard work and employing well-thought-out tactics. His former supervisors and officers describe the commander as an officer who could handle himself on the street or in a staff meeting with equal confidence.
"He's a street guy," said Officer Kai Wong, a longtime friend. "On the street, he talks to people on a one-to-one basis."
Wong recalled seeing another side of Clark in the late 1990s when Wong accompanied his boss to a weekly crime-trend meeting. The sessions -- also known as ComStat -- were often grueling as commanders were put on the spot with lots of tough questions. Clark had the answers.
"I thought, `Where did he learn to talk like that?' He talked like a college professor," Wong said. "He broke everything down."
Knocking down walls
After more than two years commanding the 47th, Clark was moved to another violent precinct, the 44th. When he arrived in early 2001, Clark felt commanders had not been paying enough attention to community concerns, and he decided to break down barriers separating the police and residents.
He removed a gate at the precinct and knocked down a concrete wall to create more space in the station for visitors. Clark moved his office to a more accessible location, even though it meant losing his private bathroom.
Clark also reduced crime in the 44th, by about 20 percent in his first year. Meanwhile, homicides fluctuated slightly.
"He is very focused," said Timothy Pearson, a precinct commander. "In New York, as long as you don't lose the three C's you'll be all right -- cops, community and crime. He had all three. He left his mark."
Six months ago, Clark was promoted to deputy chief of the narcotics division, where he has run the day-to-day operations of the department's drug-fighting efforts.
Clark said he has managed to get the most out of his troops by carefully studying the strengths, weaknesses and enthusiasm of his direct subordinates.
"It's like when you go buy a dog and you pick out the most energetic and attentive one and bring it home, man," he said. "That one usually turns out the best."
In turn, those leaders pushed officers to excel, he said.
Pointing to his record of success, Clark said he is confident that he will make Baltimore safer and is not overwhelmed by the prospect of leading a 3,300-member department.
"I don't have to speak to 3,300 officers," he said. "I only need to reach the commanders. ... I have my own way of doing things. It works. Even the guys who don't like me, they are better cops than they ever were."