San Francisco District Attorney George Gascón expressed concerns about the safety of transportation network companies Friday afternoon following the arraignment of a 26-year-old Uber driver who allegedly struck a passenger in the face with a hammer in Bernal Heights early Tuesday morning. Pacifica resident Patrick Karajah, an employee of ride service Uber, picked up three passengers about 2 a.m. Tuesday in his UberX vehicle as they were leaving a bar, Gascón said. During the ride there was a dispute as to the route that the driver was taking. Gascón said he suspected one or all of the passengers thought the driver was taking a longer route to get a larger fare. As a result of the dispute, the driver allegedly asked the two men and the woman to get out of his car near the intersection of Alemany Boulevard and Ellsworth Street, just off Interstate 280, Gascón said. Karajah allegedly proceeded to assault the male victim with a hammer. The victim was struck in the area around his eye and his injuries are considered very serious, Gascón said. Gascón said the other two passengers saw the attack but were not injured. Following the attack, the driver fled the area, Gascón said. Karajah was arrested following the attack. He was arraigned Thursday and pleaded not guilty to assault with a deadly weapon and battery causing serious bodily injury. He is out on $125,000 bail, Gascón said. Gascón said that Karajah does not appear to have a criminal record but because he was working for Uber at the time, the company could be held liable. Gascón said his office is concerned that the ride service companies' business practices “are not good for the consumer, they are not good for the community.” He said his office wants to continue to support new business models and innovations but has to balance that with protecting the community. The companies' business practices are generating safety concerns, Gascón said, but he assured the public that whatever solution is arrived at wouldn't threaten the businesses. The Uber attack followed the delivery earlier this week of a letter from the San Francisco District Attorney's Office and the Los Angeles District Attorney's Office to transportation companies Lyft, Uber and Sidecar threatening legal action over a number of unresolved issues. On Thursday, Gascón said in a statement that his office values “innovation and new modes of providing service to the public; however we need to make sure that the safety and well-being of consumers are adequately protected in the process.” Gascón said he is concerned about the metering systems used by two of the companies as well as by the companies that are operating at airports without the consent of the airports, among other issues. The letter echoes a declaration by the California Public Utilities Commission earlier this month that the instant carpooling products are illegal. Sunil Paul, the chief executive officer of the company Sidecar, received one of the letters from Gascón. Upon receiving the letter, Paul urged customers to sign a petition on Change.org asking the California Public Utilities Commission and the state's district attorney's offices “to end their campaign to stop Sidecar Shared Rides, UberPool, and Lyft Line in California.” Paul said the new carpooling features, which match drivers with passengers traveling in similar directions, are “safe and very affordable, cut down on traffic congestion and reduce pollution.” Paul said the “overzealous” regulators are “acting under pressure from big taxi companies.” Gascón said members of his own family use the transportation network services and he said he is not against the business model, but needs to protect consumers.