The New Jersey congressman's chief of staff, one of 11 men snared in a recent Montgomery County sex sting, arrived at an apartment complex expecting to meet a teenage girl, but instead was greeted by officers in the parking lot, authorities said.

Robert Decheine, 48, was charged with solicitation of a minor and remained free Thursday on $15,000 bond, court records say. U.S. Rep. Steven R. Rothman (D-N.J.) fired Decheine over the incident.

"Congressman Rothman considers this alleged criminal act to be shocking, appalling and indefensible," his office said in a statement this week.

Decheine's attorney noted that his client has not been convicted in the case.

"Mr. Decheine has just been charged at this point," Stanley Reed of Bethesda said. "He is presumed innocent."

Reed declined to comment further and said that Decheine had no comment.

"No one ever suspected this type of behavior," said a friend of Decheine's who is a Hill staffer and who spoke on condition of anonymity because he was not authorized to discuss the matter. "It broadsided all of Bob's friends. . . . We're hoping that he is exonerated."

Decheine had carved out a reputation as someone willing to listen but not afraid to flex his muscle, his friend said, calling Decheine "a very smart political operative."

Gaithersburg police spokesman Dan Lane said Decheine was picked up as part of a sting led by Gaithersburg police and involving Montgomery police, Maryland state police and the FBI.

Police placed a personal advertisement with a photo of a young-looking woman on a Web site, Lane said. When men responded to the ad, undercover police would communicate with them by phone, e-mail or text messages, Lane said. At some point during the correspondence, an undercover officer told the suspects she was 15, Lane said.

Police set up phony meetings at an apartment complex on McCausland Place in Gaithersburg. From Nov. 15-19, they arrested 11 men who came to the complex, Lane said.

All were picked up in the parking lot and taken to Gaithersburg police headquarters for questioning. "They were shocked to see us," Lane said Thursday.

Lane said Decheine was the only suspect of such notoriety.

morsed@washpost.com