Update 3: Final sequence of events: as we expected, cops confuse name, CNN reports it, and media goes wild. From the AP: "Adam Lanza's older brother, Ryan, 24, of Hoboken, N.J., is being questioned by police, said the first official. Earlier, a law enforcement official mistakenly transposed the brothers' first names."
Update 2: the reason for the confusion is that the first name reported today by CNN and promptly carried by the rest of the media, Ryan Lanza, may be incorrect, and should likely be Adam Lanza . At this point until the police correctly identify the suspect it is probably best to ignore all further updates from CNN or otherwise on the matter.
— CNN Breaking News (@cnnbrk) December 14, 2012 
Update: there is confusion as to whether this is indeed the correct Lanza or not. As The Inquisitor reports :
A screenshot circulating on Twitter purports to have recent updates from Lanza denying a connection to the Sandy Hook Elementary shooting:
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The shooter has been idenitifed by CNN as one Ryan Lanza, 24, out of New Jersey. A quick Facebook scan has identified one Mr. Ryan Lanza in the 18-24 year old age group, out of Hoboken, NJ who lists Newtown, CT as his home city. There is one unconfirmed account of a suspect born in Newtown, CT and currently living in Hoboken, NJ, although it appears it is not the suspect in question. The mother of the suspect was a teacher at the Sandy Hook school, and she is among the dead.