The earliest coverage I can find is from the Buffalo NY Commercial, 13 April 1861:
EXCITING AFFAIR IN TROY -- ARREST OF PROF. ANDERSON THE MAGICIAN
Professor ANDERSON, whose necromantic entertainments in Buffalo will be remembered by many of our readers, was arrested in Troy Wednesday on the complain of a journeyman barber, who had been employed for a day previous, in circulating stories alike ridiculous and false, with reference to the Professor's character. The latter was promptly discharged on proving his complete innocence of the charge, and, meeting the barber in the afternoon, gave him an unmerciful drubbing.
The Troy newspapers don't seem to be available online, but coverage from them was widely reprinted, and more details came out (from the New York Evening Express, April 13):
Conspiracy against Professor Anderson -- He is Arrested and Discharged -- His Traducer Beaten
(From the Troy Daily Times, 11th.)
The purlieus of the Police Court were considerably excited, yesterday, by the arrest of Prof. Anderson, the great magician, for an alleged criminal connection with a young girl about fourteen years of age, an apple vendor in this city, who, it was charged, had been inveigled into his room at Rand's Hall, and there compelled to submit to the lascivious desires of the magician. The story, it appears, was started by a barber employed in the shop on the second floor of Rand's Hall, who pretended to know all about this last and greatest trick of the wonderful Professor. The story reached the ears of Constable McMulkin, of the Ninth Ward, who, without any process, and upon his individual authority, took Prof A. into custody. The Professor was not detained in jail or compelled to submit to any restraint, except so far as an arrest on a parole of honor and an exposure on a false charge would inconvenience and harass any man. The barber told a very ridiculous story in relation to the girl and the Wizard, so preposterous, indeed, that no one capable of weighing facts would have paid any attention to him. He was arrested some time in the forenoon, and his examination was to take place at 3 o'clock in the afternoon before Justice Landon.
In the interim, between the arrest and examination, the officer and the prosecutor of Mr. Anderson were occupied in finding the girl. She was apprehended, and taken before the Justice at the examination, she told her story -- having had no interview whatever with Professor Anderson meantime -- substantially to the effect that she visited Rand's Hall to sell her trinkets; she went up into Prof. A.'s room and requested him to purchase some of the articles, which he declined doing. She remained some time in his presence, when he asked her what she wanted she then took out a subscription paper, which she was circulating for the purpose of raising money to buy her a sewing machine, and asked him to subscribe. This he did, and gave her a dollar, when she went away. The Professor in his conversation apart from the girl, detailed the circumstance of their interview identically the same as she had done, and the barber who alleged the charge, and the constable who was so officious in arresting Mr. Anderson, being unable to state more than general allegations, Justice London promptly dismissed the Wizard, and intimated to him the right he possessed of causing the arrest of the officer on a charge of false imprisonment.
Of course Professor A. was positive of his acquittal of the base charge which designing men had laid against him. Every circumstance in the case pointed to his innocence, and it is even said that the charge was a trumped up affair, intended to extort money from him, in the expectation that he would rather give $100 than submit to an exposure of this character. But the parties mistook their man and Professor Anderson stands acquitted before the community of the dishonorable act. Professor A. was so incensed by his arrest, that afterward meeting the barber who was the original cause of his prosecution, he so far forgot himself as to take the law in his own hands, and give the man a most unmerciful beating. He belabored him severely, disfiguring his face and eyes, and leaving upon him other evidences of a not very affectionate regard.