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A suburb outside of Boston remains on edge after a string of serial attacks left nearly a dozen men clubbed over the head, as police are “dramatically increasing” patrols and offered a $5,000 reward Tuesday for information that helps pinpoint who might be responsible.

"There is definitely a fear factor in our city right now. We've never experienced anything like this," said Waltham Police Detective Sgt. Steve McCarthy told reporters Tuesday.

"I'd be lying to you if I said I'm not losing sleep at night, you know, coming into work. This is an awful situation," McCarthy continued. "But I'm very confident that we're gonna work through this and we're gonna find the people, or persons, that are responsible for this."

MASSACHUSETTS POLICE SEARCH FOR SUSPECT IN STRING OF 10 'RANDOM, UNPROVOKED' STREET ATTACKS

The apparently random string of attacks begun Nov. 10 at the Gardencrest apartment complex in Waltham, a Massachusetts suburb of some 60,000 residents about 11 miles west of Boston, but has spread to the downtown area. The victims have all been men who were walking alone, but they range in age from 20 to the mid-40s and are of various ethnic backgrounds, Police Chief Keith MacPherson said.

On Thursday, Waltham police released two new clips from security footage showing a suspect on the night of Nov. 25. The first video shows the suspect in the distance running south on Prospect Street before turning west onto Bedford Street. The second video shows the same suspect from a different angle as he walks west down Bedford Street.

In an interview with The Boston Globe, Emerson Antonio Aroche Paz described how he was struck twice in the head around 10 p.m. on Nov. 25. He said he wiped the blood from his face to see his assailant, but the person had fled. He called 911 and went to the hospital.

“My nose broke. Part of my head is cracked,” Aroche Paz said. “But my brain is fine.”

Emerson Antonio Aroche Paz was struck in the head twice around 10 p.m. Nov. 25, he <a href="https://www.bostonglobe.com/2020/12/01/metro/waltham-authorities-offer-5000-reward-information-person-or-persons-responsible-spate-random-attacks/">told The Boston Globe.</a> (Facebook) 

Emerson Antonio Aroche Paz was struck in the head twice around 10 p.m. Nov. 25, he told The Boston Globe. (Facebook) 

“My God, we're scared," Waltham resident Amos Frederick, 37, told the Associated Press on Wednesday as he walked through the complex. “All of us stay indoors except during the day. If someone is just walking to their car, we watch out for them."

MacPherson said police are looking into a “couple persons of interest,” but investigators cannot yet confirm whether one or multiple suspects may be responsible for the attacks.

WV COP SHOT IN FACE PULLED FROM LIFE SUPPORT, ORGANS TO BE DONATED

Authorities are offering a $5,000 reward for information that leads to an arrest and conviction.

Before the latest footage was cleared, police on Saturday released two different clips from closer angles showing someone in a dark hoodie pulled tightly around his face running and walking down an undisclosed street.

The person or persons responsible for the attacks appear to be “lying in wait,” intentionally selecting victims who are distracted, before then approaching their target from behind, striking them in the head with some sort of blunt force object, MacPherson said.

Police released two security camera clips showing the male suspect believed to be responsible for a string of 10 assaults since Nov.10. (Waltham, MA Police Department)

Police released two security camera clips showing the male suspect believed to be responsible for a string of 10 assaults since Nov.10. (Waltham, MA Police Department)

Several victims were hit so hard that they were knocked to the ground. Some required hospitalization for serious injuries, including orbital facial fractures, a fractured nose, and lacerations to the face, MacPherson said.

One victim was walking a dog. One was getting into a vehicle. A U.S. mail carrier was attacked while going door-to-door. The latest attack happened the day after Thanksgiving.

“The motive is somewhat in question but it appears to be a thrill of the assault, or someone who’s very violent and enjoys seeing someone hurt by this,” MacPherson said Tuesday. “There’s never been a robbery. It’s always been just an assault and the assailant takes off.”

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In response to the attacks, police have stepped up patrols with both uniformed and plainclothes officers and are also using drones for aerial surveillance. Waltham police consulted with Boston police to determine whether the attacks could be some sort of gang initiation, but that does not appear to be the case.

The Associated Press contributed to this report.