The chief executive of a startup in San Francisco’s Mid-Market area called for more police on the streets Wednesday after one of his employees witnessed a brutal beating steps from their office.

The worker on Tuesday captured a video as he was returning from lunch of a man brutally striking another man. His boss, Geoffrey Woo, runs a company called Hvmn (pronounced “human”) with 10 employees. This year the startup moved from a co-working space in the Financial District to a three-story walk-up at 38 Mason St. for more space.

Tech investment and tax breaks have brought thousands of high-paying jobs and some new restaurants and other businesses to the neighborhood, but critics say the push to revitalize the area hasn’t substantially changed a challenging street milieu of poverty, homelessness and violent crime.

Request for help @sfgov @SFPD @LondonBreed. My coworker took this video this morning outside our 38 Mason St office. I’m a small business owner, and it’s dangerous & unsafe for my employees to be walking in a war zone. Days with police presence are much better. We need more. pic.twitter.com/zwWdO2d4Ub — Geoffrey Woo (@geoffreywoo) December 19, 2018

The seven-second video, taken Tuesday afternoon and tweeted by Woo that night, shows a man in gray sweats and a baseball hat stomping a man’s head on the ground. The injured man, whose face is mostly obscured, recoils after being hit and then lies motionless. No one immediately intervenes, and the perpetrator warns bystanders to back off.

“I’m a small business owner, and it’s dangerous and unsafe for my employees to be walking in a war zone,” Woo tweeted, mentioning the Twitter accounts of Mayor London Breed, the police and the city to catch their attention. “Days with police presence are much better. We need more.” Woo repeated his call Wednesday, urging “a more consistent presence.”

The employee who captured the video requested anonymity over concern for his safety.

The San Francisco Police Department is investigating, according to Officer Robert Rueca, a police spokesman.

He would not say if either of the men in the video has been identified. Anybody with additional information is asked to contact the police, he said.

Woo said police visited the Hvmn office Wednesday.

Employees had been stopping him in hallways to talk about the incident, he said. He tweeted the video to help bring attention to violent crime on San Francisco’s streets.

“We spend more time in the office than we do in our homes,” Woo said. “I feel some responsibility not just for my safety but the personal safety of my employees coming in and trying to make a living.”

Woo faced criticism on Twitter for his choice of words, particularly labeling the neighborhood a “war zone.” One user, Aaron Clark, who identified himself as a Berkeley resident, described the tweet as sensational.

“The Tenderloin is bad and needs help. But fearmongering isn’t the answer,” the user wrote. Another said tech-driven gentrification was part of the problem.

“When you decide to leave (and you will), please don’t bring the politics that caused this to your next destination,” said Mike Roberto, a Texas resident.

For others, though, the beating that occurred on a busy sidewalk midday underscored continued challenges in the Mid-Market area, where other companies have moved out amid safety concerns. Music streaming company Spotify recently decamped from three floors of office space at 988 Market St., ending its lease early. The change was motivated in part because some Spotify workers felt unsafe, said two former employees who requested anonymity to avoid repercussions from former or current employers. Last year, a Spotify worker was slapped in the face by a homeless person near the office, the former employees said.

Spotify relocated to the Merchants Exchange Building in the Financial District in November.

Mid-Market is part of the Tenderloin Police District, which reports some of the city’s highest numbers of violent crimes. The number of aggravated assaults in the Tenderloin, for example, rose 7 percent in October compared with the year before. For that category of crime, it is on par with much larger police districts, including the Mission, Bayview and Northern stations.

The increase in aggravated assault in the Tenderloin stands in contrast with citywide figures; reports of aggravated assault in San Francisco fell to 210 in October, down 14 percent year over year. San Francisco is overall one of the safest cities in the nation. Its violent crime rate ranks 75th out of 298 cities with a population of 100,000 or more.

Last month, Breed directed the Police Department to ramp up foot patrols around the Mid-Market corridor — the city’s latest effort to revitalize the area and rid it of the drug pushers that have settled there. Ten additional officers, two sergeants and a lieutenant were reassigned to patrol Tenderloin streets.

The mayor’s office did not immediately respond to a request for comment.

Woo said employees often see beat cops within blocks of the office, patrolling BART and Muni Metro’s Powell Street Station. He would like to see officers venture one block over, to the intersection of Mason and Turk Streets.

Rueca, the police spokesman, said the department has officers on patrol in the Mid-Market and Tenderloin neighborhoods around the clock. However, it’s hard to be everywhere at once, he said.

“We do our best to patrol in areas where incidents occur,” Rueca said. “Unfortunately, incidents still occur.”

San Francisco Chronicle staff writer Roland Li contributed to this report.