Chilling CCTV footage emerged of a man in a box just meters from a police officer wheeling the corpses of two dismembered children.
The kid, identified as Edgar Z, was arrested in Mexico City on suspicion of murdering two teenage boys, Hector Efrain, 14, and Alan Yair, 12.
Security video released by the police demonstrates how the police officer watching became frightened.
Before his trolley wheels start to jam, Edgar Z is seen moving the boxes along the pavement and he ends up crashing into a container on the side of the road.
He spends a few seconds battling to right the trolley and continuing his ride.
His arrest and the discovery of the remains of two missing children, including a human arm , shoulder and ear, are said to have caused the mishap after they spilled from the boxes onto the tarmac.
A police officer is standing just a few feet away as the remarkable scene unfolds in the upper left-hand corner of the video screened on Mexican TV.
So far, three men have been arrested over the murders of 14-year-old Hector Efrain and 12-year-old Alan Yair, who were last seen on 28 October.
The youngsters were identified as street sweet sellers who, by selling drugs on the side, were thought to have begun working for a local crime boss.
The kids are said to have been beaten, according to local sources, before being dismembered.
After his faux pas with the boxes, Edgar Z is said to have been arrested when police went to assist him and noticed his macabre contents.
Union Tepito, a criminal group founded in 2009 linked to drug trafficking, abduction, extorting and murder, was identified as the gang said to be behind the horrific crimes.
Also arrested was Edgar’s boss, Jose David N, alias El Chayan.
Only Baltazar N, a 25-year-old said to have guarded the room where the murdered youngsters were tortured in the Union Tepito operations center, was called the third detainee.
No specifics have yet been disclosed about the reason for the murder of the youngsters.
“Claudia Sheinbaum, head of the government of Mexico City, said:” It is extremely painful and very serious what happened to the two children in our city.
“It’s unfair that these crimes are committed by criminal groups.”