Authorities investigating the robbery and fatal stabbing of an 18-year-old Olney man at the Woodley Park Metro station are looking for at least three more people, a homicide detective testified in D.C. Superior Court on Monday.

The detective, Robert Arrington Jr., said the three can be seen in footage of the attack from Metro security cameras but have yet to be identified. His testimony came during the second day of a preliminary hearing for four of the nine teenagers charged in the Nov. 17 robbery and slaying of Olijawon Griffin.

The incident began when Griffin was robbed of a $400 Helly Hansen jacket, an iPhone and a baseball cap near an Exxon gas station in Adams Morgan. Griffin was fatally stabbed about 20 minutes later at the Woodley Park Metro station when he and a group of his friends happened upon those who they thought had robbed him.

One of the nine defendants at Monday’s hearing, Chavez Tyrek Meyers, 17, has been charged as an adult with murder. He is accused of approaching Griffin from behind and stabbing him in the chest. Four others have been charged as adults with armed robbery, including three who were in court Monday: Deon Jefferson, Immanuel Swann and Gary Maye. The fourth charged with robbery, Tyvell Smith, is scheduled to have his hearing Dec. 10. The four youngest suspects, two 15-year-olds and two 16-year-olds, have been charged as juveniles and were not present.

In addition to revealing the search for three additional people, Arrington provided further details on a knife that one of the defendants said he saw Griffin holding immediately after he was robbed in Adams Morgan. Arrington quoted the defendant, whom he did not identify, as saying he saw Griffin holding a knife at his side as he and the other defendants ran away after robbing Griffin.

Arrington testified that there was no evidence that Griffin had a knife at the Woodley Park Metro station when he and his friends confronted his alleged robbers. Griffin and his friends walked to the Metro, which was about a half-mile from where he was robbed. Authorities said they recovered two knives, one of them bloody, and a .45-caliber pistol from behind a locker at the Metro station.

Prosecutors played a video from the Metro security cameras. Beau Perrizo, a detective with the Metro Transit Police, identified each of five defendants visible in the video and what they were wearing. One of them, Perrizo said, was wearing a Helly Hansen jacket of his own. According to court papers, Jefferson was wearing Griffin’s Helly Hansen jacket when Griffin arrived at the Metro.

During a preliminary hearing last week, prosecutors played another 16-second Metro security video of the altercation. The videos, Perrizo said, show the suspects in the Metro station and the attack against Griffin and his friend. As the new video played, Maye, Swann, Jefferson and Meyers leaned together to watch it on a monitor. At one point, Maye, looking at the monitor, smiled and shook his head.

The preliminary hearing is scheduled to continue Tuesday in Judge Ronna L. Beck’s courtroom. Beck is scheduled to decide, based on the evidence presented, whether the teens should be released from D.C. jail as they await trial.