Investigators believe the homicides are connected and have been examining whether Sanchez’s appearance at the courthouse could have led to his death, according to the officials, who spoke on condition of anonymity because they are not authorized to discuss the case.

It was unclear what, if anything, Sanchez told authorities about the June 5 shooting, which left another man injured. Although the officials told the Globe that Sanchez was brought to court in the hope he would testify, Jake Wark, spokesman for Suffolk District Attorney Daniel F. Conley, said that Sanchez was “not a cooperating witness’’ in Martinez’s homicide or any other slaying.

Diomedes Pimentel, who lost his daughter and grandson in the shooting, said a relative told him that the two went to court together but was unaware of what transpired there.

They died “savagely,’’ he said. “You never think something like this can happen.’’

The killing of Sanchez and his mother, Elvira Pimentel, 43, has renewed concerns about the risks of providing police with information about crimes, a longstanding problem in many Boston neighborhoods. It also underscores the struggle of witnesses who must decide whether to come forward when they live in neighborhoods where even the perception that one has cooperated with authorities can be deadly.

Was he referring to the Boston Miracle of nearly 15 years ago? Or to the peaceful celebration that followed the Bruins’ triumph this summer while angry fans took to the streets in Vancouver? Is any recent Boston unrest comparable to the London riots, where disenfranchised youths have seized on concerns about police violence to launch mayhem, burning storefronts and stealing flat-screen TVs?

Those involved in Boston’s celebrated 1990s anticrime program were unsurprised, saying the London uprising points to a civil breakdown that demands a new strategy for community policing.

“Violence is deeply rooted in how people feel like they’ve been denied in society. It’s more than just criminality,’’ said the Rev. Jeffrey Brown, executive director of the Ten Point Coalition, a faith-based community group that works with young people and that partnered with government and law enforcement officials to reduce violence in Boston.