Following the thefts, Atomic Wallet tweeted that they were aware of the reports of wallet compromises, and that they were attempting to learn more about the attacks, but had not yet confirmed any method of attack. They've since taken down the wallet software download page, likely out of concern that the software itself has been compromised.
Crypto sleuth zachxbt compiled a list of reported compromised Atomic Wallets, finding that multiple individuals lost multiple millions in the attack. The largest known individual theft so far involved almost $8 million in USDT (Tether); other individuals lost $2.8 million in USDT and 1,897 ETH (~$3.5 million).
Users of Atomic Wallet have been advised to transfer their assets to other wallets.
On June 6, both zachxbt and blockchain research group Elliptic speculated that the laundering strategy by the thieves resembled that of the North Korea-linked Lazarus Group, which has been responsible for other major crypto thefts.