Editor’s note: A previous version of this story misstated how the two missing boys know each other. The story has been updated.

NEW YORK (PIX11) – The older sister of 11-year-old Alfa Ousmane Barrie was tearful on the phone Tuesday morning, desperate for information after her little brother didn’t come home from his Harlem charter school on Friday.

“This was the first time this ever happened,” Fatima Diallo said about her brother, who is the youngest of six children.

Diallo and police believe Barrie may be with a friend, 13-year-old Garrett (Man Man) Warren, who’s also been missing for days. Barrie lives in the Bronx and Warren lives in Upper Manhattan, according to police.

Both families have placed flyers near Democracy Prep Middle School on West 133rd Street in Harlem, where Barrie attends classes. Warren attends a different school, according to police.

The poster featuring Barrie’s photo says he was last seen wearing a Democracy Prep navy blue uniform shirt, grey pants, and a black senior hoodie with the number 18 on the back and the name “Aissata.” Barrie is 5 feet 2 inches tall and weighs about 100 pounds, authorities said.

Missing posters for Alfa Ousmane Barrie, left, and Garrett Warren, right. (credit: Handouts)

The two boys were observed on surveillance video leaving one of their homes and then walking together at 145th Street and Lenox Avenue in Harlem around 6 p.m. Friday, according to the NYPD.

“We are trying to identify everybody who was with them,” said Brian Gill, deputy chief at Detective Borough Manhattan North. “We need to speak to every single person who was with them … We want to talk to their classmates. We’ve been in contact with their schools.”

The Harlem location was the last place Barrie was seen. Warren was last seen in front of his home on Saturday around 1:30 a.m., according to an NYPD missing persons report.

Warren has black hair, brown eyes and is 6 feet tall and 215 pounds, authorities said. He was last seen wearing a tan hooded sweatshirt with a white T-shirt underneath, black jeans and blue/black Jordan sneakers.

“Find my grandson. This is not like him. He is not a little boy who just up and disappears for days and days,” said Candy Bojng, Warren’s grandmother.

The NYPD called on the public to come forward with any information that could help find the missing boys.

“There are millions of eyes and ears in our city, and we are asking all of them right now to help us find these children,” said Ruel Stephenson, assistant chief at Patrol Borough Manhattan North.

Submit tips to police by calling Crime Stoppers at 1-800-577-TIPS (8477), visiting crimestoppers.nypdonline.org, downloading the NYPD Crime Stoppers mobile app, or texting 274637 (CRIMES) then entering TIP577. Spanish-speaking callers are asked to dial 1-888-57-PISTA (74782).