According to Lam, the most critical information he possesses is the names of those who've bought books from his bookstore in the past, most of whom are from the mainland. He was able to return Hong Kong on bail, in the company of two officials, because he promised he would hand that list over to the Chinese government.
He obtained the hard drive that kept the information and just as he was set to return to China, he said he thought of his supporters and changed mind. The list however, might have been leaked to the government through Lee Po, another bookseller.
Lam said he didn't seek help from the Hong Kong government because of their pro-mainland attitude in recent years.
As of Thursday, Gui Minhai is the last bookseller that's still being detained. His daughter testified in DC about her father's captiviity.
Lam looked healthy and remained calm throughout the 100-minute press conference, which is available only in Cantonese.
Lam also said that before the press conference he met with Lee Po, another of the five booksellers, who told him that he was “taken away against his will." That's at odds with Lee's March statement, when he said he went to mainland "voluntarily" to assist the investigation on the bookstore.
Lam's girlfriend remains in mainland China on bail, according to local Chinese-language outlet The Initium.