Surveillance video released in the hunt for the Brown University gunman shows a stocky, masked figure whose walk shifts from calm to restless and awkward — behavior a body language expert says signals classic “anomalies” seen in people acting with malicious intent.

“From a behavioral perspective, looking around, pacing and placing hands behind the back have been associated with many loitering-type behaviors and active surveillance of the environment rather than traveling through an area,” said Susan Constantine, who is also a certified and licensed trainer in threat-assessment behavior. “This is consistent with behavior anomalies in persons of malintent.”

She told Fox News Digital that he appeared “focused on a destination” in early clips, which were recorded before the shooting.

“He’s scouting and in rehearsal,” she said, regarding the earlier clips. “He is walking the paths out, could be timing routes, CCTV cameras.”

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But he soon raised red flags and displayed “a really important marker” showing the unique way that he walks, she said.

“When crossing the street in the middle of the block, the subject’s pace quickens, and he seems to be in a hurry. His gait becomes hurried, and a more waddling gait can be seen. He has his right hand in his pocket. It is not possible to determine if he has a weapon or not, but concealing the hand and object within it inside a pocket is a form of concealment. The subject’s right lower leg also bows outward as he walks, resulting in an abnormal gait.”

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Police in Providence, Rhode Island, have released multiple video clips and other surveillance images in the hope that members of the public can help identify the person of interest, who remains at large more than 72 hours after a mass shooting in a lecture hall Saturday.

“Taken as a whole, the characteristics of a heavy or stocky build, behavioral changes, hyper awareness of surroundings, pacing movements, bulky clothing, facial and hand concealment, and a hurried pace with a waddle as he walks and his right lower leg bowing out as he walks are characteristics that could be used to track this person in the future,” Constantine said.

In particular, she said the videos show his right leg bowing inward while his toe points outward as he walks. And he could be right-handed, she said, based on how he walks with one hand in his pocket and the other swinging freely.

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“These are behavior traits that cannot be controlled,” she explained. “That’s what’s causing him to waddle. Could be a knee injury.”

The attack left two students dead, identified as Ella Cook of Alabama and Mukhammad Aziz Umurzokov of Virginia, and nine injured.

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Authorities said during a Monday news briefing that they recovered 9mm casings at the scene.

Police released additional surveillance clips Tuesday afternoon, one of which showed the purported person of interest walking right by officers as they responded moments after the shooting. The additional footage, in higher resolution, shows the person is not as stocky as initially expected, Constantine said, especially during a portion where he is seen running along a picket fence.

“He is concealing something under his jacket,” she said. “He is not as stocky as first viewed.”

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The gunman remains at large.

Anyone with information is asked to call Providence police at 401-272-3121 or submit tips to the FBI online.