In a tweet, he wrote: "There are injuries from people running from what they thought were gunshots". People began running from the area and police keeping watch over the festivities heard revellers shouting there was a man with a gun.
The 38-year-old has been charged with illegal possession of a BB gun, carrying a unsafe weapon, and disorderly conduct.
Rivera added that seven people were sent to hospitals with non-life threatening injuries and emergency crews treated others for minor injuries at the scene after a crowd fled from the area.
As the officers got closer, someone in the crowd pointed to Singh and said he had a gun in his bag.
Ashley Smith, the president of the tournament organizers, Capital Pride Alliance, remained defiant. "Upon observing the indicated bag, which was partially open, Officer Maio observed what appeared to be the body and trigger of a silver handgun", says the report.
A police report - cited by the Associated Press news agency - said he took the weapon out after noticing someone "hitting his significant other".
"About a of the contributors within the crowd mentioned there turned into once a person with a gun and that someone had fired a shot", mentioned Commander Guillermo Rivera of the Metropolitan Police Department.
The unidentified man was taken into custody during Saturday night's parade and is facing a gun possession charge, police said. USA Today quoted her saying that the fire department personnel were on the scene to treat minor injuries due to the reports of a shooting.
The man, named in USA media as Aftabjit Singh, allegedly sent the crowd running through the streets of Washington, DC, on Saturday after wielding what appeared to be a gun.
The name of the man arrested after police found a firearm near him was not immediately released.
After the chaos, Capital Pride tweeted that the parade was over but a block party would go on as scheduled.