FBI experts on Dec. 16 combed through the vicinity of a weekend mass shooting that killed two students at the elite Brown University, as the hunt for the gunman dragged into a fourth day.
Images posted by the bureau on social media showed laboratory specialists and evidence response teams conducting a forensic search on the snow-covered grounds outside the Providence, Rhode Island campus.
The shooting happened on Dec. 13, when a man with a rifle burst into a campus building where exams were underway and opened fire, before fleeing.
Providence officials screened a new video timeline at a briefing on Dec. 16 that appeared to show the person of interest walking through residential areas in the town.
"There's enhanced video footage so we are asking the public to see the body movements, the body posture... that may help you identify this individual," said the town's police chief colonel, Oscar Perez.
Perez renewed his appeal for members of the public with homes and vehicles equipped with cameras to supply footage to the police.
Two-hundred actionable tips had been received by investigators, he added.
Authorities initially detained a man in connection with the shooting, but they later released him, saying he was unconnected.
The FBI, which is offering a $50,000 reward for the suspect's capture, said he should be considered "armed and dangerous" and described him as "approximately 5 foot 8 inches with a stocky build."
On Dec. 16, Brown University called on its students who may have been in the area of the shooting to arrange for a police interview.
