"He is very regretful," police investigator Dan Östman told the TT news agency.
Under interrogation by police on Sunday, the 28-year-old man tried to explain why he didn't help his victim, who had fallen onto the tracks and was lying unconscious.
According to the police, the mean feared that he would be suspected of having pushed the victim, a 38-year-old father, onto the tracks.
"That's the reason he gave; that he was scared of being accused of having caused all of this," said Östman.
The highly-publicized case, broadcast last week on TV3's "Efterlyst" ('Wanted') television programme, took place early Sunday morning a week ago at the Sandsborg metro station, south of Stockholm.
After being robbed, the victim was run over by a train and seriously injured, but survived.
According to Östman, the suspect had considered turning himself in, but police managed to catch him before he had the chance.
The 28-year-old suspect, referred to last week by police as "Sweden's most wanted man", was arrested in the north Stockholm suburb of Akalla on Friday night.
Two other men were apprehended in conjunction with the arrest on suspicions of trading stolen goods.
However, both were released on Saturday and are no longer suspected of any crimes, said Östman.
The suspected subway robber remains under arrest and prosecutors have until Tuesday to file a motion to have him held on remand.
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