WASHINGTON - While D.C. police search frantically for a teenager wanted for 21 violent robberies and assaults, residents of the Columbia Heights neighborhood are asking how he could be set free again.

The suspect, 18-year old Michael Richardson, is believed to have assaulted and robbed D.C. resident Jeff Weinstein at the Columbia Heights Metro Station. Weinstein said he can't believe the suspect is not in jail. "It was mainly shocking, shocking," he said.

Richardson allegedly approached people leaving the Metro Station, grabbed them from behind, and threw them to the ground and beat them until they surrendered their valuables.

After arresting Richardson for the third time, police in Columbia Heights sent out an alert. They told residents to e-mail the office of the Attorney General urging Richardson be kept behind bars and not sent to a halfway house, where he had already walked away to allegedly resume his string of muggings. Before the onslaught of e-mails arrived, however, Richardson already had been released.

On Monday, police raided Richardson's aunts home, but none of his family members said they know where he could be. "I don't know where he is -- try over on 14th Street. That's where he [is], on 14th Street," the suspect's aunt told ABC 7 / NewsChannel 8 reporter Stephen Tschida.

Columbia Heights residents hope the police find the suspect soon. "I hope they find him soon because somebody is going to get killed next," said Beth Shannon.

"It's unbelievable there has got to be some way to keep him because he is just going to go out and do it again," said Guy Heard.

Representatives of the U.S. Attorneys office and the office of the Attorney General for D.C. are now offering up explanations for Richardson's release, essentially saying someone made a mistake.