The Mattapan massacre case will continue.

Prosecutors and defense attorneys will have to work on revising their strategies and a new jury will have to decide the fate Dwayne Moore, 34, of Mattapan.

Moore is accused of fatally shooting four people, including a 2-year-old boy and his mother, and severely injuring a fifth person during a robbery in 2010.

After deliberating seven days, a jury acquitted him of a drug charge and said they were deadlocked on the other charges against him. A judge declared a mistrial.

Prosecutors said they would schedule a new trial date next week to continue their prosecution of Moore.

But their strategy will likely have to change as legal experts said the defense attorneys were apparently successful in planting doubt in the minds of the jurors.

William D. Kickham, a Boston criminal defense lawyer, said prosecutors took a gamble by using Kimani Washington as their key witness. Washington testified in return for a plea deal for his role in the home invasion and robbery.

“The backfire potential or downside potential is … quite high and I think that these outcomes illustrate that point,” Kickham said.

Finding a new, impartial jury that has not been exposed to the constant media coverage of the trial and the shootings will be a difficult task, Kickham said.

Washington a free man

Edward Washington, 32, will soon be a free man.

The Dorchester man who was put on trial for his role in the murder of four people was found not guilty Thursday of all charges he faced.

Prosecutors alleged that he did not pull the trigger, but he participated in the robbery and provided Dwayne Moore with a gun.

Suffolk District Attorney Daniel Conley admitted in a statement Thursday that prosecutors knew convicting Washington would be difficult.

“It always is when the charge is felony murder and the theory is joint culpability,” Conley said.

Reaction

Not only were family members upset by Thursday’s outcome, but the potential for retribution apparently worried city officials:

As soon as the first “not guilty” verdict was read inside Suffolk Superior Court this afternoon, some family members and friends of the Mattapan massacre victims jumped up, screamed and had to be escorted out of the courtroom.

Reaction from the community was also strong on Twitter where one person posted “Just because u get away in court dont mean ur gonna get away in the street.”

Mayor Thomas Menino urged those who were grieving to seek guidance from a trusted friend or spiritual advisor and “not act on raw emotion.”

“Our city needs to heal. We need to be good to one another and take care of our neighbors to stop the cycle of violence,” Menino said in a statement.

Police officers were dispatched to the Mattapan neighborhood where the shootings occurred as a precaution, said Police Commissioner Ed Davis.

“Officers will be in the area walking and talking with residents. … It is imperative as a community to respect (the justice) process and allow it to work,” Davis said.

Below, families of the victims react to the verdict: