Thomas ran up to the vehicle and confronted Christopher Tucker, the man who police say tried to kidnap Shamir as the youth was grabbing a snack at the Korner Deli on West Chester Pike near Keystone Avenue, about 20 yards from home.
"I'm just a dad protecting my child; he's my firstborn," Thomas said. "I'd do that for any of my kids."
And so he lost himself in the moment, he said. He pounded on the driver's window, demanding that he let his son go.
Instead of driving away at the sight of the angry father, the punk in the car decided to get out and "throw his hands up," according to Thomas.
By the time Upper Darby police arrived, Thomas had subdued the bruised and battered Tucker after giving him a thrashing.
"I'm normally a coolheaded guy," Thomas said, "but he brought the fight out of me.
"When you jeopardize my family, that's a big problem."
Tucker, of 60th Street near Arch in West Philadelphia, was charged with kidnapping, unlawful restraint of a juvenile, false imprisonment and related offenses, Upper Darby Police Superintendent Michael Chitwood said.
"This was truly a stranger abduction that was foiled by the family," Chitwood said.
Most frightening, at least for Thomas' girlfriend, Mikala Martin, was that it almost wasn't foiled.
Shamir frequents the Korner Deli almost every day. The staff knows him, Martin and Thomas well. So it wasn't unusual, Martin said, for the boy to walk there unattended.
What was unusual, however, was the amount of time it took him to return. And when Martin and Thomas went looking for him, they were told by the deli's staff that the boy's "uncle" had come to pick him up.
Problem is, none of the boy's uncles live in the area. And when a frantic Martin ran outside, she said, she saw a car parked just feet from the door with Shamir trapped inside.
"My heart sank; I felt helpless," she said. "All I could do was scream for his dad to come out."
According to police, Tucker had plied the youth with candy and cookies, and was intoxicated when officers took him into custody after his scuffle with Thomas.
He has prior arrests for assault and drugs, police said.
"Why do you take a 6-year-old out of a store, buy him candy and say you're his uncle unless you're going to do something mean or nasty?" Chitwood said. "There was a major tragedy that was foiled here."
Martin agreed, adding that she won't be letting Shamir out of her sight anytime soon.
"Now, I don't feel safe unless I'm watching him," she said. "Even though this guy is locked up, I don't know who else is out there."
Thomas said that he and Martin would walk Shamir to the spot where his school bus picks him up in the morning, and accompany him on any future trips to the Korner Deli.
"It could've been different if I didn't get there in time," Thomas said.
"You have to put your life on the line for your kids, no matter the cost."
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