A Renfe train driver, Antonio Acedo, 36, died when his train struck the rear of an Iryo train at 124 mph in Spain.
The collision killed at least 69 people, while rescuers continue to search for bodies and locate missing relatives.
Among the missing are a headmaster, a composer, a TV presenter and a food-bank volunteer.
More than 100 individuals sustained injuries, some critical, after several carriages derailed and toppled down an embankment.
Both Antonio and his fellow trainee driver, Daniel Muñoz Cob, 31, who sat beside him in the cockpit, were killed.
Antonio's family called him a "hero" after learning he pulled the emergency brake, which they say saved hundreds of passengers.
Audio from Madrid's control centre shows the moment the error occurred. The controller instructed Antonio to "Resume [driving] at normal speed." Antonio replied, "At normal speed?" and the controller answered, "Yeah."
The driver was not warned that another train ahead was stranded due to equipment problems, despite the control centre's awareness.
Antonio was an active member of the Izquierda Española party and had warned about deteriorating rail infrastructure and chronic under-funding.
Journalist Paula Fraga said, "Antonio was one of the frontline workers who sounded the alarm over deteriorating rail infrastructure, one of those ignored and dismissed workers who died because officials refused to listen."
Party leader Guillermo del Valle described him as "a good man" and a "cautious, kind and exemplary colleague."
On social media, Antonio had written, "I imagine that when we reach the end, if we look back and find happiness, we aren't saddened to leave."
The Spanish Confederation of Business Organizations confirmed that former politician Fátima Báñez, who served as minister for employment and social security from 2011 to 2018, also died in the tragedy.
A 24-year-old athlete and a 36-year-old policeman were among the dead.
Runner Julieta Gallego, representing AD Sprint, was described by Raúl Chapado, president of the Royal Spanish Athletics Federation, as having had her life "unjustly extinguished."
Police officer José Manuel Chacón, 36, was returning to Seville when the crash killed him; he had married four months earlier.
Die-hard Atletico Madrid fan David Martinez Mendez remains missing, with his family recalling him as "cheerful and devoted to his loved ones."
Engineer David Reina Reguera, 22, called his family at 8.30 a.m., less than thirty minutes before the accident; his whereabouts are still unknown.
Architect Alexandra García Bartolomé also vanished after speaking to her family about twenty minutes before the collision while travelling to Seville for business.
