Families run for their lives as father is killed in front of his son in shooting at youth football game in the US (VIDEO)

A gunman killed a father and wounded his seven-year-old son in one of four shootings in the Jacksonville area over the weekend, opening fire near a park hosting a youth football game amid horrific scenes captured on a livestream.

The youth teams were lining up to play when gunshots were suddenly heard nearby, sending the children and their families diving to the floor and running in panic as coaches and parents reacted with confusion and told them to go to ground.

Police are now searching for the suspected murderer of a 27-year-old father, who was not seen in the chilling footage, following the attack at Arlington Heights Elementary School.

Reports showed the field strewn with footballs and debris after the terrified crowd fled the scene.

Lieutenant JD Stronko, of the Jacksonville Sheriff's Office, said that police were searching for a black male suspect with a grey hoodie and a mask who had exited the rear of an SUV and begun to shoot in the direction of the victims.

An onlooker told local news teams that his 22-year-old nephew had attempted to use his first aid skills by applying pressure to the gunshot wound that killed the man but had been unable to save him, although his son has reportedly survived.

"You saw the little boy, he was on the ground," they said, asking to remain anonymous. "He got shot. His dad got shot."

Lenny Curry, the Mayor of Jacksonville, said that the spate of "senseless violence" in the region over a horror weekend would not be tolerated.

"To the victims and their families, I extend my deepest sympathy," he added.

"To the seven-year-old child shot at the Arlington Athletic Association, my family and I are praying for your full recovery.

"As a father and former coach of youth athletes, this senseless act of violence is particularly distressing."

The footage of the chaos begins in innocuous fashion with the man holding the camera introducing the game as "highly anticipated".

A rattle of shots can then clearly be heard from the distance, sending the players scurrying away as the man points out: "Somebody is shooting."

They later added: "This is f*cking ridiculous. This is f*cking bullsh*t."