Boston police, along with Massachusetts and federal law enforcement authorities, continue to search for the suspects in shooting rampage that left a toddler and three adults dead.

Authorities say five people were shot in the city's Mattapan neighborhood early Tuesday. One of the victims remains clinging to life, but police have said he is not expected to survive.

Relatives say the toddler killed was a 2-year-old boy who was shot while being held in his mother's arms. His mother was one of the victims.

Police have not released the victims' names and have not revealed a possible motive.

The shooting drew outrage from Boston Mayor Tom Menino who called the killer or killers "cowards."