Yǒu rén tíqián gěi tāmen bàoxìn, jǐngchá pū le gè kōng.
Someone tipped them off in advance, so the police came up empty-handed.
Tips
usage
报信 can be neutral (to notify) or carry the implication of tipping off someone in advance, sometimes to help them evade consequences. Context determines whether it is innocent or illicit.
