D.C. police arrested an 18-year-old Friday and charged him with a fatal shooting in June on the edge of Capitol Hill, according to authorities. Police said the motive was to steal the victim’s newly purchased motor scooter.

Troy Q. Robinson of Southeast Washington was charged with second-degree murder. He was arrested Friday about 12:40 a.m. by the D.C. and housing authority police. Authorities said they are searching for a second suspect.

The shooting occurred about 1:25 a.m. June 24 behind an apartment building in the 700 block of 12th Street SE, near the Potomac-Gardens Housing development and the Potomac Avenue Metro station.

The victim, Tywayne Thompson, 25, of Southeast Washington was shot with two guns and was wounded in the back, groin and left leg. He died at Howard University Hospital. Police said they found four 9mm shell casings and two .45-caliber shell casings at the scene.

In charging documents filed in D.C. Superior Court, police said witnesses told them that two men had conspired to rob Thompson of the gray and black motor scooter he had bought the day he was killed. Police said the found the scooter, and dried blood, two days after the shooting, hidden behind a white shed in the apartment complex parking lot.

Witnesses told police that they had heard the two men bragging about the shooting and arguing over who shot the victim in a particular body part, according to the court document. According to police, one of the men told the other, “Finish him off,” after they both had shot Thompson in the legs.

Police said in the court documents that one witness had come forward to try to claim the $25,000 reward offered for information leading to an arrest and conviction.