The gunman entered Las Dominicanas M & M Salon in Casselberry shortly after 11 a.m., police spokeswoman Sara Brady said. Two women escaped the salon.
Police have not identified the victims or the gunman. Brady said the shooting appears to be part of a domestic dispute.
The phone rang unanswered at the salon. A video posted on the salon's website has a woman explaining in Spanish the services offered at the salon for men and women.
Brady said the wounded woman was being treated at an Orlando hospital. Her condition was not immediately released.
A witness told the Orlando Sentinel he heard gunshots before seeing the gunman take off.
"We saw the guy with the gun in his hand ... coming this way ... on foot with the gun in his hand," said Juan Diaz, who was at a nearby store at the time of the shooting. He said he went into the salon once the gunman left and saw "a bunch of dead bodies."
Casselberry is about 15 miles northeast of Orlando.
A year ago in Southern California, an angry ex-husband donned a bulletproof vest before killing his ex-wife and six of her fellow stylists and patrons at a hair salon, police said. Scott Dekraai is also accused of killing a man in the parking lot. He is awaiting trial on murder charges.
Laboy reported from Miami.