MIAMI (NYTIMES) - A gunman shot and killed a toddler and his grandmother before fatally shooting himself Thursday morning (June 10) in a Publix grocery store in Palm Beach county in the southern US state of Florida, authorities said.

Deputies from the Palm Beach County Sheriff's Office found their bodies near the produce section of the store in Royal Palm Beach just before 11.40am, a Sheriff's Office spokesperson said.

The names of the victims and the gunman were not immediately released. The child, a boy, would have turned 2 later this month, said Teri Barbera, the sheriff's spokesperson.

"We don't have any idea who the male is at this time," Barbera said, referring to the gunman.

Later Thursday, authorities said there was no known relationship between the gunman and the two victims. A motive for the shooting had not been determined.

Investigators were reviewing security video from the store and talking to witnesses, Barbera said.

"What we are doing now is documenting the scene," Barbera said. "We're trying to determine what led up to the shooting."

The store is in a shopping centre called the Crossroads, off Okeechobee Boulevard and Royal Palm Beach Boulevard. The village of Royal Palm Beach is about 12 miles (19km) west of Palm Beach, Florida.

"Our thoughts are with those who are impacted by this tragedy," Maria Brous, a spokesperson for Publix, said in a statement. "We are cooperating with the local law enforcement."

Helicopter footage from local TV stations showed a heavy police presence outside the store, with about 15 police cars at the scene.

Juan Guardia, a Publix customer, told reporters at the scene that he was in the store's deli area when he heard gunshots. A store employee yelled, "a shooter, a shooter!" he said.

Joey Mendoza told The South Florida Sun Sentinel that he was pulling into the parking lot on his way to the Publix when he saw police cruisers and officers, some in tactical gear, approaching the store.

"I saw them running in, I didn't get out of the vehicle," he said. "They just kept coming.

Cruiser after cruiser, ambulance after ambulance, fire truck after fire truck."

Officials at the nearby Crestwood Middle School briefly locked the school down, according to the School District of Palm Beach County.

An employee at a Dollar Tree store in the shopping complex said the plaza was locked down while the authorities investigated the shooting.

Melissa McKinlay, a Palm Beach County commissioner who represents the area where the shooting took place, said on Twitter that "we've become too numb to gun violence."

She asked the public "to mourn for the loss of these lives and pray for those inside of Publix who witnessed this tragedy."

This was the latest shooting in south Florida in recent days. On Sunday, three people were killed and five wounded at a graduation party in Miami.

Two people were killed and at least 20 wounded a week earlier when three shooters fired "indiscriminately" into a crowd outside a concert in the Miami area, police said.

Mass shootings have taken place across the United States this year in a surge of violence that President Joe Biden has branded an "epidemic".