"We've been following it up actively," Johnson said. "Today, we got lucky. The tip was called in and it panned out."
A 17-year-old Hagerstown girl who was in the room was charged with harboring a fugitive and accessory after the fact, police said.
The charges against Crosby stem from an Oct. 24 shooting that injured a 16-year-old girl in the 400 block of North Potomac Street. The unidentified teenager was hit in the upper left leg by one of seven gunshots fired through the door of an apartment, according to police.
Two men began beating on the front door of Apartment 8 at 441 N. Potomac St. and attempted to kick it down, according to police.
During a lull, one of the four people inside the apartment looked out through the peephole of the door and saw two men.
Detectives George Knight and George Brandt will continue the investigation, Johnson said.
"They are attempting to determine the motive behind that crime," he said.
Crosby, who is also known as "Special" or "Eric," was charged with attempted second-degree murder, four counts of first-degree assault, four counts of second-degree assault, four counts of reckless endangerment, use of a handgun in commission of a felony, wearing or carrying a handgun and discharge of a firearm within city limits.
A State Police warrant also charges Crosby with three counts of first-degree assault, three counts of second-degree assault, reckless endangerment, robbery, theft and use of handgun in commission of a felony.
Those charges stem from a Sept. 25 incident in Hancock, police said.
The crimes occurred shortly before 10 p.m., according to police. A Cumberland, Md., woman met a man briefly at the Hardee's restaurant in Hancock to discuss a drug transaction and then followed him to the intersection of McKinley Drive and Tollgate Ridge Road, police said.
The man told the woman he was looking for the "stash" and then turned and struck her in the head with his handgun, police said.
He then pointed a semiautomatic pistol at two men who were sitting in the woman's car and demanded the keys to the vehicle.
Before driving away with two women who were in his car, the man stole about $500 from the victim, police said.
The vehicle was later discovered at the Super 8 Motel in Hagerstown.
Crosby was jailed Sunday night on $175,000 bond.
The juvenile was held at the Washington County Juvenile Detention Center.