A full jury has been chosen in the trial of a Boston man accused of ambushing and killing a Rochester police officer. Kelvin Vickers is charged with murder, attempted murder, weapons offenses and arson, prosecutors say.

Twelve jurors were seated with four alternates chosen by late morning on Wednesday.

Last July, Rochester Police Officers Anthony Mazurkiewicz and Sino Seng found themselves in the middle of a gang-related dispute over marijuana territory, according to investigators. The officers were conducting undercover surveillance in an unmarked police van on Bauman Street near Laser Street when they were ambushed and shot, authorities say.

Mazurkiewicz was killed, while Seng was injured in the attack. Vickers was eventually apprehended by officers in an abandoned house near the scene of the shooting.

“I really feel that we have a jury that will fairly and impartially review this case over the next four weeks," Monroe County District Attorney Sandra Doorley said. "So I’m very satisfied.”

“I feel that we’ve picked a fair and impartial group of jurors," Defense Attorney Michael Schiano said. "Again, it’s very difficult. We went through almost 250 jurors in this case and we think we’ve found 12 jurors and four alternates who we think are going to be fair and impartial to this case.”

The process has moved quickly enough that the trial will get underway with opening statements at 9:30 a.m. Thursday. It was originally scheduled to begin on Monday, Sept. 25.

“We’ll be giving the jury a timeline, you know, what occurred when and in what order," Doorley said. "Because we want them to be able to follow the testimony. I think it’s really important in this case to present it in a chronological fashion so that the jury understands what happened from point A to point B.”

“On any opening, we try to get these jurors to keep an open mind," Schiano said. "You’ve heard so much from the media about what this case is about, but they haven't heard any evidence what-so-ever. They haven’t heard what the law is in this case. They haven’t heard what they are going to be charged with the law at the end of the case. So we tell them to keep an open mind and listen to the evidence, listen to both the direct and cross examination and don’t come with any judgment until the end of the case.”

The court is expected to be packed with family members and law enforcement.