A spokesman for Medical City Healthcare, which was treating several victims at three trauma facilities, said the ages of the injured ranged from 5 to 61.

The gunfire erupted around 3:30 p.m. at the Allen Premium Outlets as throngs of shoppers filled the outdoor mall, which is about 25 miles north of Dallas and has more than 120 stores. Videos circulating on social media show people dashing for shelter or running through a parking lot as loud popping noises can be heard in the background.

Seven people, including the gunman, were pronounced dead at the mall. Officials could account for at least nine people who were transported to hospitals, but more victims may have been taken in private vehicles, the Allen fire chief, Jonathan Boyd, said. Two of those died later. Three were in critical condition and four in stable condition.

A video circulating on social media appeared to show the gunman, lying on the ground, clad in black and equipped with what appeared to be a tactical vest, multiple rounds of ammunition and a long gun.

“We all want the victims and their families impacted by this tragedy to know that we will wrap our arms around you and we are here for you,” Ken Fulk, the mayor of Allen, said at a news conference. “We know you are grieving. We are grieving. Rest assured, the nation and the world are also grieving. Allen is a proud and safe city, which makes today’s senseless act of violence even more shocking.”