ATLANTA -- It's been nearly a month since a group of pedestrians was severely beaten on Edgewood Avenue, SE, near Boulevard.

Now, the race to find the men involved is intensifying as loved ones of the most seriously wounded victim plead for tipsters to come forward.

The sudden, unprovoked and savage attack by a gang of four was in the dark, April 22, outside the clubs and restaurants just east of downtown Atlanta.

Security camera video shows, according to police, three of the attackers on the prowl moments before they pummeled three unsuspecting men with their firsts. The men had simply been walking together down the street. Seconds later, one of the men, Mark Calub, was on the street with head injuries, barely holding on to life.

"I'm still in shock, there was no purpose to it other than, I think, to attack," said Adam, a friend of Calub. Adam asked not to be identified by his full name as a precaution, since the attackers are still on the loose.

Adam and other friends said Calub, 36, is from California and was visiting Atlanta for the first time. He was rushed to the hospital in critical condition. He has since been stabilized.

"We want to bring these people to justice," Adam said. "To make sure this doesn't happen to anybody again."

Friends are now leading a social media manhunt for the suspects, and raising money for a reward. They're also raising money to support Calub, a corporate environmental health and safety specialist, who lives to be with others.

"Well loved by his family and friends," Adam said.

Just about every photo on Calub's Facebook page shows him with friends - in events he organized to be with his friends.

"That's it, it's like Mark loves to bring people together," Adam said. "He's really caring, he's really thoughtful, he loves to plan and organize cool events."

► Related: Suspects leave man 'fighting for life' after 'senseless' Edgewood assault

They're coming together again for him and trying to help Atlanta police. But it's a case that confounds detectives.

"Four African American gentlemen walked up and circled the three of them," Major Adam Lee, III said. "It just seems like a case of gratuitous violence. There was no provocation, from what they're saying, and it just happened suddenly.... The motive appears to be just violence - just a feeling to hurt someone for no good reason at all."

Major Lee said even though the video is not the clearest, it does show that one of the suspects was wearing a jersey with the number 34 on the back. And the video shows that another suspect may have had an injured right hand as he was running away after the attacks. The getaway car may be a maroon Nissan Armada.

"The investigators are working hard," Lee said. "We just need help.... [The victims] didn't do anything to deserve this. They were just enjoying a night out in the City of Atlanta."

The Crime Stoppers reward for anonymous tips in the case is now up to $5,000 thanks to Calub's friends coming together again for their friend - the same friend who is always bringing them together.

"We just came together to make sure he knows he's loved," Adam said. "People care about him and we're there for him."

Police also say there is a chance that the attackers are from out-of-town. That could be why no one from Metro Atlanta has recognized anyone in the video, yet. That possibility makes it even more important, now, police say, that people share that video on social media, nationwide.

Background on Mark Calub, from friends who are seeking support for him and trying to encourage tipsters to help police:

"Mark grew up in Southern CA where he was enrolled in honors classes and actively involved in social groups and performing arts. He attended University of California, Irvine where received a Bachelor’s degree in Chemistry and Environmental Analysis. Soon after graduating, he worked for Boeing as a Safety Engineer while simultaneously pursuing his MBA in Business Administration, Management.

He later moved to San Francisco to work as a Safety, Health and Environmental Specialist. He continued his studies and received a Master’s degree in Environmental Management at the University of San Francisco.

Outside of his work and scholastic activities, Mark led and participated in many student organizations. He was also an active member in his church leading church youth activities and even traveled to Kenya to teach music education to the underprivileged. No one is as busy as Mark but he always managed to make time for those he loved and cared about."

Family Statement:

"Mark was visiting a friend in Atlanta for the first time, and out of nowhere he and his friends were attacked as they walked down the street. What was supposed to be an enjoyable and memorable trip turned into a nightmare. Mark is a well-loved brother, son and friend to so many, and we are beyond devastated by this tragedy. Please help us spread the news so that those responsible are brought to justice so they can’t hurt others like Mark again. We're so heartbroken that anyone would do this to him. He is always full of life and an awesome person to be around. If anyone knows anything about this attack, please contact the Atlanta Police Department."

To offer anonymous tips in the case and qualify for a possible reward of up to $5,000, contact:

Crime Stoppers Atlanta 404-577-TIPS (404-577-8477)

For more information:

Bring Justice for Mark Facebook Page

YouCaring Fundraising Page for Mark Calub's hospital costs