Wright had been committed to the Oak Hill House for troubled teens in late 1996 on an unrelated matter and on Dec. 31, he ran away from there and later stole a car, ending up in Baltimore, police said.
It was there Wright allegedly met up with several other youths, and they stole another vehicle and began a series of alleged robberies and thefts that led them back to Washington County on Jan. 5, accoding to police.
State police arrested Wright, then 16, on charges of armed robbery, two counts of first-degree assault, using a handgun in the commission of a felony, theft of $2,901, and conspiracy to commit armed robbery.
The same charges have now been levied against the other two, police said.
Wright was automatically waived to adult court because of the seriousness of the charges and because he was over 16.
Hacker was charged in January and was also treated as an adult.
The latest teen charged, being only 15, was too young for automatic waiver but can be waived later if a judge rules the criteria have been met for such an action.
A pellet handgun was taken into custody Thursday when the latest teen was picked up, police said.
State police said two ski-masked robbers entered the grocery at 14845 National Pike in Clear Spring, displayed handguns to the two clerks and demanded money.
In his statement to police, Hacker told of the four youths riding around in a stolen vehicle on Jan. 5, first robbing a woman in Howard County and then another in Harford County, police said.
Netting $290 in those two robberies, they spent that money on beer, whiskey and marijuana, police said.
Then the four youths traveled to Hagerstown amidst talk of committing a robbery, police said.