Police yesterday charged a man with intimidating a witness who testified before the Sean Bell grand jury, officials said.

Melvin Cordero, 46, was arrested at 3:45 p.m. and accused of intimidating a witness, tampering with a witness, and coercion, the Queens district attorney’s office said. The witness, whom other press outlets identified as Roberto Manaya, worked under Mr. Cordero at Meridian Cleaning, police said.

Mr. Manaya came forward in the final moments of the grand jury proceedings to say that he had witnessed the shootings.

The president of the Detectives Endowment Association, Michael Palladino, said Mr. Manaya heard Detective Gescard Isnora identify himself as a police officer and that he saw a fourth, unidentified man fire several rounds. Mr. Manaya’s unexpected appearance drew criticism from the Reverend Al Sharpton, who said the testimony was suspicious.

Mr. Cordero allegedly told Mr. Manaya not to come forward because it would hurt the company and possibly his standing as an employee, a law enforcement source said.

Detective Isnora and two other detectives, Michael Oliver and Marc Cooper, were indicted in the shooting of Bell on March 16. Detectives Isnora and Oliver face manslaughter charges in the case; Detective Cooper faces a charge of reckless endangerment.

Port Authority police were informed about Mr. Cordero’s threats by another supervisor at the cleaning company, Port Authority officials said.

“This office will not tolerate the intimidation of, or tampering with, witnesses and is committed to the vigorous prosecution of those who engage in such conduct,” the Queens district attorney, Richard Brown, said in a statement. Mr. Cordero faces up to four years in prison if convicted of intimidating a witness, and up to one year in prison for each charge of tampering with a witness and coercion, the district attorney’s office said.