At first, the two children playing outside the Oak Creek Sikh temple just before Sunday services thought they were hearing fireworks.
But then Amanat Singh, 9, and her brother, Abhay Singh, 11, saw a man exit from a vehicle in front of the holy site.
“He got out of a cab and he fast-walked and hit two people who were getting into their car," Amanat said in an interview with ABC News.
What the pair did next may very well have saved some from the tragedy that would ultimately claim the lives of six Milwaukee Sikhs before gunman Wade Michael Page turned his weapon on himself.
The two children ran into the temple kitchen to warn about the danger outside.
“I’m like: There’s a guy with a gun! Hide! Hide!" Abhay told ABC.
Amanat said she felt very scared -- scared that "everyone was going to die" -- but the quick-thinking move may have made a difference for the dozen or so worshippers who were able to escape the carnage.
However, the duo's heroism was not the only act of valor on display that Sunday.
Lt. Brian Murphy, 51, was one of the first officers on the scene of the shooting, and was almost immediately ambushed by Page, who shot him nine times from point blank range.
As the officer lay bleeding, he waved his fellow cops on, telling them to help the civilian victims first. Murphy, who is still recovering from his injuries, was awarded $10,000 dollars from Sikhs for Justice, in recognition of his selflessness, the Journal Sentinel reports.
And in an interview with The Huffington Post, the nephew of one of the victims detailed how his uncle's actions inside the temple may also have prevented further deaths.
Harpreet Singh's uncle, Satwant Kaleka, 62, struggled with the attacker in two separate incidents, before succumbing to his gunshot wounds.
"[The shooter] went in, my uncle engaged with him and tried to tackle him, and was shot in lower abdomen and leg," Singh told HuffPost. "[The shooter] went to kitchen where he was confronted by my uncle again, and I believe he died at that spot."
The Morning Email helps you start your workday with everything you need to know: breaking news, entertainment and a dash of fun. Learn more