The shooting happened on Saturday at the Milwaukee Public Schools South Stadium around 1:02 p.m.
First responders immediealty checked and cleared the stadium of any threat to the families.
Milwaukee police said they found a 47-year-old man with a gunshot wound. He was rushed to the hospital where he later died.
A 37-year-old man was taken into custody, however police said he is not a suspect in the homicide.
It is unknown what led to the deadly shooting.
A neighbor who lives near the stadium told ABC Milwaukee affiliate WISN that sge saw a man laying on the ground and people trying to help him as parents and children rushed away from the scene.
Milwaukee Public Schools expressed gratitude to "first responders for their quick response to the situation."
Anyone with any information is asked to contact Milwaukee police.