Collins Chinese Dictionary Plus (3rd edition), 2011:
不了了之 bù liǎo liǎo zhī leave unresolved
- 由于(於)找不到嫌疑人,这(這)个(個)案件只能不了了之了。 Yóuyú zhǎo bù dào xiányírén,zhège ànjiàn zhǐ néng bù liǎo liǎo zhī le. Since the suspect hasn't been found, the case simply had to be left unresolved.