Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
intĕremptor (-emt-), ōris, m. [interimo], one who destroys or kills, a slayer, murderer (post-Aug.): fratris, Vell. 2, 129, 1: eri, Sen. Ep. 70, 12: puellae, Val. Max. 6, 1, 2.