"She did tell us that there was a delivery," San Jose Police Chief William Landsdowne told the CBS News Early Show. "We were able to back track that to the restaurant to bring it back to the house, which was a key piece of the information that she gave us."
Computer records provided to police by the owner of a nearby store helped police trace the order to David Montiel Cruz, 24.
In addition, the worker who delivered the pizza was participating in the national Amber Alert notification system launched to help find the girl. The worker said he even advised Cruz to be on the lookout for the missing child.
Cruz was taken into custody Monday in a pre-dawn raid at the home of a friend less than a mile from where he allegedly kidnapped the girl on Friday after brutally beating her mother and brother.
The scene was captured on a neighbor's surveillance camera.
Police conducted an extensive search over the weekend for the intruder after he kidnapped the girl as she returned home alone from school Friday. The girl surfaced at a convenience store Sunday night and was said to be resting after her ordeal.
A SWAT team raided a San Jose home where he was staying with a friend and found him hiding in the attic, Deputy Chief Rob Davis said. He tried to fight off officers and was briefly hospitalized after a police dog bit him.
Cruz was being booked on suspicion of kidnapping, burglary, robbery, assault with a deadly weapon and sexual assault, Assistant Chief Thomas Wheatley said. Police said he will likely be charged Tuesday or early Wednesday; his arraignment was tentatively scheduled for Wednesday.
Police said Monday they believe Cruz knew of the fourth-grade girl through one of her former schoolmates, though neither the girl nor her family knew him.
"The motive appears to be a sexual abduction, because we don't see any other motive at this point," Assistant Chief Thomas Wheatley told The Associated Press on Monday.
Davis said police believed all along the abduction was not a random crime: not only did the attacker wait for the girl to return home, he twice told her mother "you know what I want" as he beat her before screeching off.
Cruz resembled a police sketch of the suspect and had injuries consistent with what police expected from the struggle he had with the girl's mother, Lansdowne said.
"We're very confident this is the right person," Lansdowne said.
"We have sufficient physical evidence now to tie him to the original kidnapping scene," Landsdowne said. "We have some fingerprints that puts it together for us. We're absolutely confident that we'll be able to charge him to the fullest extent of the law, to prosecute him. He'll get a life sentence."
On Monday, the girl's mother, her face still swollen and bruised from Friday's attack, thanked authorities, the media and her neighbors before she began to choke back tears.
"I want to tell all mothers not to let your kids walk alone on the street, no matter how secure it is," the girl's mother said in Spanish. "Because when you feel you lose a child, I think it is like the feeling of dying."
The girl's ordeal ended Sunday night, when she suddenly appeared at the Eastside Market in East Palo Alto, about 30 miles north of her home. "She was crying and scared," said Isa Yasin, the owner of the shop.
The girl was probably dropped off by her captor, who might have been frightened by the attention the case received, Davis said.
The kidnapper told the girl not to call police, so she first tried to call her mother, though she was too shaken to dial the number. Yasin realized who the girl was after talking briefly with her and called police.
Though the abducted girl's name was initially widely reported in the media, it is CBS policy to omit the names of victims of sex offenses.