A major emergency response was sent to the scene, near Bedford Road, after reports of a “casualty” on the tracks at around 7pm on October 14.
It followed reports two children of the same age were seen on the tracks.
Emergency services remained on the tracks for several hours and rail services were cancelled on the line as police, ambulance and fire crews carried out investigations.
It was confirmed last night a “person” had died following an incident on the tracks.
Today, the ECHO understands two children, thought to be 12-years-old, were reported to be on the live lines, with one of them being killed.
An emergency switch-off of the tracks was requested by British Transport Police (BTP) who rushed to deal with the incident.
Since the tragic incident, ECHO readers have posted heartwarming tributes on social media for the little boy.
On Facebook, Debbie Cutler said: “So sad. Thinking of the family and friends of this 12-year- old. RIP little one.”
Catherine Pye also added: “Very sad time for the family this is a terrible thing to happen. God bless, heartbreaking.”
Kirsty Marie McCormick added: “Aww this is so sad for all involved. His/her mate is going to suffer after seeing this. RIP little one thinking of your family!
“But I also hope this story helps other kids to realise the danger of been on a railway!”
Many people also passed on thoughtful messages to the little boy’s family.
Angela Flaherty said: “Heartbreaking reading this my thoughts to his family.”
Rosa Doran also added: “So sad and way too young to fly with the Angels. Thinking of his family and his mate.”
Teresa O’Connell also said: “So sad. Thinking of his mum and dad, family and friends – just heart breaking reading this.”
Marva King added: “12- years- old tragic.”
If you have been affected by any of the details mentioned in this story there are people who can help you.
Most people grieve when they lose something or someone important to them.
The way grief affects you depends on lots of things, including what kind of loss you have suffered, your upbringing, your beliefs or religion, your age, your relationships, and your physical and mental health.
Grieving is a totally normal process but there are way to get help if you need support.
Your GP is a good place to start. They can give you advice about other support services, refer you to a counsellor, or prescribe medication if needed.
Or you can contact support organisations directly, such as Cruse Bereavement Care (0808 808 1677) Samaritans (116 123) or Love Jasmine.
The stretch from Sandhills to Waterloo on the Northern Line was isolated as workers rushed to reach the body.
Track staff also attended the scene to inspect fencing around the area.
Last night, British Transport Police said they were called “following reports of a casualty on the tracks.”
A spokesman for the force said: “Paramedics also attended however sadly a person was pronounced dead at the scene.
“The incident is not being treated as suspicious and a file will be prepared for the coroner.”
A large emergency service presence could be seen at Bedford Road, as neighbours reported seeing a fire engine, ambulance and police officers at the scene.
Pictures showed officers taking photographs of an underpass underneath the rail tracks and an area was also cordoned off.
Rail services were suspended between Sandhills and Hall Road while emergency services investigated the incident.
A spokesman for Merseyside Police told the ECHO: “Following reports of a concern for safety for a person in the area officers were called to Bedford Road in Bootle.”
The gender of the child is not yet confirmed. British Transport Police and Merseyrail were contacted for comment.