Authorities took the unusual step of releasing the images on Tuesday – and made the arrest in the evening after, it was reported, that someone recognised the person in the video.
Police in Emden, Lower Saxony, have not confirmed a report in mass circulation daily Bild that a witness came forward to identify the man seen in the video dressed in dark clothing in the car park.
“We will be working through the investigation calmly, there is no more that we can say,” the spokesman said.
Footage of the man was taken from the car park on Saturday after the body of the girl, identified only as Lena, was discovered by a security guard in a multi-story car park adjacent to a multiplex cinema.
She had gone out with a boy of the same age at 5 p.m. on Saturday to feed ducks. The pair had cycled into the car park, adjacent to a multiplex cinema, between 5:30pm and 7pm. Her body was found some hours later.
"I can say that the crime was sexually motivated," said police spokesman Brandt on Monday. Police are yet to disclose the exact cause of death, but are treating it as a murder case.
The town of Emden has put up a €10,000 reward for information leading to the arrest of the attacker. So far 75 people have come forward to the police offering information.
Around 1,500 people from the small town gathered in front of the train station on Monday evening for a minute's silence.