Around 8:15 a.m. on Saturday, Keith Williams took out a loaded .357 revolver at Blue Hill Avenue and McLellan Street and began firing into a crowd of people waiting for the J'Ouvert parade, assistant Suffolk County District Attorney Mark Lee said today.

One of the bullets hit Dawnn Jaffier in the head a block away at Charlotte Street, killing her, Lee said. Another bullet traveled more than four blocks down Blue Hill Avenue, hitting another woman in the leg as she sat on a curb with her friends.

A Dorchester District Court judge ordered Williams, 18, held without bail today on charges he murdered Jaffier, 28, of Brighton. As Lee recited the case against him, Williams stood behind a door so he could hear the charges but so that Jaffier's family, seated in the front row of the First Session courtroom, could not see him no matter how far they craned their necks.

Lee said after shooting his gun, Williams and two pals ran down McLellan and turned onto Drummond, where Williams tried to hide the gun in a yard. Police, aided by a large number of witnesses who had spotted the trio, quickly pointed police to them and they were detained soon after, Lee said.

Lee said ballistic tests on the bullet recovered from Jaffier and on the bullet recovered from the American Legion victim showed a match with the gun police recovered.

Top BPD officials - Supt. in Chief Robert Gross, Chief of Investigative Services Robert Merner, Deputy Superintendent Robert Brown and Deputy Superintendent Bernard O'Rourke - all attended the arraignment. Police Commissioner William Evans was at a simultaneous press conference with DA Dan Conley to announce the charges against Williams.

In a statement, Conley said: "Today’s arraignment of Keith Williams on murder charges marks a major step in the investigation into Dawnn Jaffier’s homicide, but I want to be clear – it is not the last step. The investigation does not stop here, and we can’t afford for potential witnesses to become complacent now that a suspect has been identified. We’ve gotten some helpful information from the public over the past few days, but we know there are others out there with information that could prove extremely valuable to this case.

"I want to address those witnesses directly. If you have specific information about this homicide, or even more general observations about individuals in the area at the time it occurred, please come forward. Investigators have been working this case around the clock to gather ballistics, commercial video surveillance, and other evidence, but they still need witnesses who can say what they heard, what they saw, and what they know."