We have observed an intense high-energy component in an inclusive $^4$He(stopped $K^-$, $d$) spectrum. For back-to-back $Lambda d$ pairs a prominent event cluster has been found just below the $m_{^4textrm{He}}+m_{K^-}-m_{n}$ mass threshold in the $Lambda d$ invariant mass spectrum of $Lambda dn$ events, which is evidence for a three-nucleon absorption process of $K^-$ in $^4$He. In addition, an appreciable strength is revealed below $sim$3220 MeV/$c^2$. Well separated $Sigma^0 dn$ events show a peak similar to the case of $Lambda dn$.
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