OAKLAND -- An Oakland man who says he was beaten unconscious by an on-duty city worker filed a lawsuit Tuesday seeking unspecified damages from the city.

Joshua Daniels was walking home from the drugstore at 8:30 a.m. Aug. 18, 2013, when he was threatened and later attacked by a city maintenance worker in Frank Ogawa Plaza, according to the complaint filed in federal court.

The dispute began after Daniels had tossed his chewing gum into what he believed was a garbage bin, but might have been a city maintenance cart, according to the complaint.

Daniels began using his phone to videotape the altercation after the worker, identified as Sonny Hightower, threatened to beat him up if he didn't leave the public plaza, according to the complaint. Hightower then slapped the phone out of Daniels hand, "grabbed (his) shirt collar and forcefully punched (him) multiple times on the side of (his) face and head," according to the complaint.

Daniels suffered a broken eye socket and nose, according to the complaint.

City Attorney Barbara Parker had not yet received a copy of the lawsuit and could not comment on it, her Chief of Staff Alex Katz said. Public Works spokeswoman Kristine Shaff declined to comment as to how Hightower, who according to the complaint was on probation at the time of the incident, got a job with the city.

Sources said that Hightower was fired following the incident and had his probation revoked.