It is a regular challenge faced by homicide detectives in New York City’s most violent precincts: getting witnesses and even victims to give useful information about shooting suspects.

Never was that more starkly clear than on Monday, as the police in Brooklyn tried to figure out who shot and killed a 1-year-old boy, Antiq Hennis, in his stroller the night before. The police said that Antiq’s father, Anthony Hennis, who was pushing the stroller, was most likely the intended target of the bullets and that they believed he may know who fired them. But if that is so, Mr. Hennis is so far not helping to catch the killer of his son.

“He’s not answered questions,” the police commissioner, Raymond W. Kelly, said.

Mr. Hennis, a 22-year-old with a history of drug arrests, including for selling heroin, would not answer questions from a reporter on Monday. A rail-thin man whose angular shoulders protruded from a white undershirt, he stood amid friends on the porch of his home on Bristol Street in Brownsville, near the shooting scene. “My son is gone,” he said softly to himself. “There’s pictures of him everywhere, but my son is gone.”

News of Antiq’s death shuddered through Brownsville, where despite a decrease in shootings so far this year, local gang disputes still lead to gunfire.